scholarly journals ANALISIS PENGARUH PENETRASI MEDAN LISTRIK LINTANG TINGGI KE LINTANG RENDAH TERHADAP IONOSFER SAAT BADAI GEOMAGNET (ANALYSIS OF THE ELECTRIC FIELD PENETRATION EFFECT FROM HIGH TO LOW LATITUDES ON THE IONOSPHERE DURING GEOMAGNETIC STORM)

2018 ◽  
Vol 14 (2) ◽  
pp. 97
Author(s):  
Anwar Santoso ◽  
Dadang Nurmali ◽  
Mira Juangsih ◽  
Iyus Edi Rusnadi ◽  
Sri Ekawati ◽  
...  
Keyword(s):  
Electric Field ◽  
Electric Current ◽  
High Latitude ◽  
Delay Time ◽  
Geomagnetic Storms ◽  
Equatorial Electrojet ◽  
Minimum Point ◽  
Low Latitude ◽  
Dst Index ◽  
Low Latitudes

The influence of geomagnetic storms on the ionosphere in the equatorial and low latitudes can be either rising or falling value of the value foF2 with the different response delay time. The difference in response is one of them allegedly influenced by the modification of Equatorial Electrojet (EEJ) generated by the penetration of high latitude electric field towards the low latitude electric field and the equator. Therefore, this paper analyzes the influence of the high latitude penetration of electric current to the low latitude electric current towards the ionosphere response to Indonesia's current geomagnetic storms using the data foF2 BPAA Sumedang (SMD; 6,910 S; 106,830E geographic coordinates or 16,550 S; 179,950 E magnetic coordinates) and data from the Biak geomagnetic field station (BIK; 1,080 S; 136,050 E geographic coordinates or  9,730 S; 207,390 E magnetic coordinates) in 2000-2001. The result showed that the injection of the electric field of the high latitudes to lower latitudes causing foF2 BPAA Sumedang to be disturbed. Onset of the foF2 disturbance in BPAA Sumedang started coincide with EEJ(HBIK-HDRW) and reached its minimum point with a time delay between 0 to 4 hours before and after Dst index reached the minimum point. For a delay time of 0 to 4 hours after the Dst index reached the minimum point, the results were in accordance with the research results from the prior research. However, for the time difference of between 0 to 4 hours before the Dst index reached the minimum point, the results differ from their results. AbstrakPengaruh badai geomagnet terhadap ionosfer di ekuator dan lintang rendah berupa naiknya nilai foF2 atau turunnya nilai foF2 dengan waktu tunda respon berbeda-beda. Perbedaan respon tersebut salah satunya diduga dipengaruhi oleh modifikasi Equatorial electrojet (EEJ) yang dihasilkan oleh penetrasi medan listrik lintang tinggi sampai daerah lintang rendah dan ekuator. Oleh karena itu, dalam makalah ini dilakukan analisis pengaruh penetrasi arus listrik lintang tinggi ke lintang rendah terhadap ionosfer saat badai geomagnet menggunakan data foF2 dari Balai Pengamatan Antariksa dan Atmosfer (BPAA) Sumedang (SMD; 6,910 LS; 106,830 BT koordinat geografis atau 16,550 LS; 179,950 BT koordinat magnet) dan data medan geomagnet dari stasiun Biak (BIK; 1,080 LS; 136,050 BT koordinat geografis atau 9,730 LS; 207,390 BT koordinat magnet) tahun 2000-2001. Hasilnya diperoleh bahwa penetrasi medan listrik dari lintang tinggi ke lintang lebih rendah Indonesia menyebabkan foF2 BPAA Sumedang terganggu. Onset gangguan foF2 BPAA Sumedang mulai terjadi bertepatan dengan EEJ(HBIK-HDRW) mencapai titik minimumnya dengan jeda waktu antara 0 sampai 4 jam sebelum dan sesudah indeks Dst mencapai minimum. Untuk beda waktu 0 sampai 4 jam sesudah indeks Dst mencapai minimum, hasilnya bersesuaian dengan hasil penelitian peneliti sebelumnya. Namun, untuk beda waktu 0 sampai 4 jam sebelum indeks Dst mencapai minimum, hasilnya merupakan temuan berbeda dari hasil mereka.

scholarly journals Obliquity forcing of low-latitude climate

2015 ◽  
Vol 11 (1) ◽  
pp. 221-241 ◽  
Author(s):  
J. H. C. Bosmans ◽  
F. J. Hilgen ◽  
E. Tuenter ◽  
L. J. Lourens
Keyword(s):  
High Latitude ◽  
Climate Model ◽  
Global Climate ◽  
Global Climate Model ◽  
Rotational Axis ◽  
Low Latitude ◽  
Low Latitudes ◽  
Paleoclimate Records ◽  
Induced Changes ◽  
The Tropics

Abstract. The influence of obliquity, the tilt of the Earth's rotational axis, on incoming solar radiation at low latitudes is small, yet many tropical and subtropical paleoclimate records reveal a clear obliquity signal. Several mechanisms have been proposed to explain this signal, such as the remote influence of high-latitude glacials, the remote effect of insolation changes at mid- to high latitudes independent of glacial cyclicity, shifts in the latitudinal extent of the tropics, and changes in latitudinal insolation gradients. Using a sophisticated coupled ocean–atmosphere global climate model, EC-Earth, without dynamical ice sheets, we performed two experiments of obliquity extremes. Our results show that obliquity-induced changes in tropical climate can occur without high-latitude ice sheet fluctuations. Furthermore, the tropical circulation changes are consistent with obliquity-induced changes in the cross-equatorial insolation gradient, implying that this gradient may be used to explain obliquity signals in low-latitude paleoclimate records instead of the classic 65° N summer insolation curve.

scholarly journals Obliquity forcing of low-latitude climate

2015 ◽  
Vol 11 (10) ◽  
pp. 1335-1346 ◽  
Author(s):  
J. H. C. Bosmans ◽  
F. J. Hilgen ◽  
E. Tuenter ◽  
L. J. Lourens
Keyword(s):  
High Latitude ◽  
Climate Model ◽  
Global Climate ◽  
Global Climate Model ◽  
Rotational Axis ◽  
Tropical Circulation ◽  
Low Latitude ◽  
Low Latitudes ◽  
Induced Changes ◽  
The Tropics

Abstract. The influence of obliquity, the tilt of the Earth's rotational axis, on incoming solar radiation at low latitudes is small, yet many tropical and subtropical palaeoclimate records reveal a clear obliquity signal. Several mechanisms have been proposed to explain this signal, such as the remote influence of high-latitude glacials, the remote effect of insolation changes at mid- to high latitudes independent of glacial cyclicity, shifts in the latitudinal extent of the tropics, and changes in latitudinal insolation gradients. Using a sophisticated coupled ocean–atmosphere global climate model, EC-Earth, without dynamical ice sheets, we performed two idealized experiments of obliquity extremes. Our results show that obliquity-induced changes in tropical climate can occur without high-latitude ice sheet fluctuations. Furthermore, the tropical circulation changes are consistent with obliquity-induced changes in the cross-equatorial insolation gradient, suggesting that this gradient may be used to explain obliquity signals in low-latitude palaeoclimate records instead of the classical 65° N summer insolation curve.

scholarly journals Induction effects of geomagnetic disturbances in the geo-electric field variations at low latitudes

2017 ◽  
Vol 35 (1) ◽  
pp. 39-51 ◽  
Author(s):  
Vafi Doumbia ◽  
Kouadio Boka ◽  
Nguessan Kouassi ◽  
Oswald Didier Franck Grodji ◽  
Christine Amory-Mazaudier ◽  
...  
Keyword(s):  
Solar Flare ◽  
Electric Field ◽  
West Africa ◽  
Geomagnetic Storm ◽  
Geomagnetic Field ◽  
Equatorial Electrojet ◽  
Geomagnetic Disturbances ◽  
The North ◽  
Low Latitudes ◽  
Dip Equator

Abstract. In this study we examined the influences of geomagnetic activity on the Earth surface electric field variations at low latitudes. During the International Equatorial Electrojet Year (IEEY) various experiments were performed along 5° W in West Africa from 1992 to 1995. Among other instruments, 10 stations equipped with magnetometers and telluric electric field lines operated along a meridian chain across the geomagnetic dip equator from November 1992 to December 1994. In the present work, the induced effects of space-weather-related geomagnetic disturbances in the equatorial electrojet (EEJ) influence area in West Africa were examined. For that purpose, variations in the north–south (Ex) and east–west (Ey) components of telluric electric field were analyzed, along with that of the three components (H,  D and Z) of the geomagnetic field during the geomagnetic storm of 17 February 1993 and the solar flare observed on 4 April 1993. The most important induction effects during these events are associated with brisk impulses like storm sudden commencement (ssc) and solar flare effect (sfe) in the geomagnetic field variations. For the moderate geomagnetic storm that occurred on 17 February 1993, with a minimum Dst index of −110 nT, the geo-electric field responses to the impulse around 11:00 LT at LAM are Ex =  520 mV km−1 and Ey =  400 mV km−1. The geo-electric field responses to the sfe that occurred around 14:30 LT on 4 April 1993 are clearly observed at different stations as well. At LAM the crest-to-crest amplitude of the geo-electric field components associated with the sfe are Ex =  550 mV km−1 and Ey =  340 mV km−1. Note that the sfe impact on the geo-electric field variations decreases with the increasing distance of the stations from the subsolar point, which is located at about 5.13° N on 4 April. This trend does not reflect the sfe increasing amplitude near the dip equator due the high Cowling conductivity in the EEJ belt.

scholarly journals Low-latitude climate change linked to high-latitude glaciation during the Late Paleozoic Ice Age: evidence from the terrigenous detrital kaolinite

2021 ◽  
Author(s):  
Peixin Zhang ◽  
Jing Lu ◽  
Minfang Yang ◽  
Longyi Shao ◽  
Ziwei Wang ◽  
...  
Keyword(s):  
Climate Change ◽  
High Latitude ◽  
Ice Age ◽  
Late Paleozoic ◽  
Humid Climate ◽  
Low Latitude ◽  
Climate Conditions ◽  
Eastern Australia ◽  
Late Paleozoic Ice Age ◽  
Low Latitudes

Abstract. The Late Paleozoic Ice Age (LPIA; ca. 360–260 million years ago) was one of the most significant glacial events in Earth history that records cycles of ice advance and retreat in southern high-latitude Gondwana and provides a deep-time perspective for climate-glaciation coevolution. However, climate records from the LIPA are poorly understood in low latitudes, particularly in the North China Plate (NCP) on the eastern Palaeo-Tethys. We address this through a detailed mineralogical study of the marine-continental sedimentary succession in the Yuzhou Coalfield from the southern NCP in which we apply Zircon U-Pb dating, biostratigraphy, and high-resolution clay mineral composition to reconstruct latest Carboniferous to early Permian chronostratigraphy and climate change. The Benxi, Taiyuan, and Shanxi formations in the study area are assigned to the Gzhelian, Asselian-Artinskian, and Kungurian-Roadian stages respectively and the Carboniferous Permian lithostratigraphy across NCP recognized as widely diachronous. Detrital micromorphology of kaolinite under scanning electron microscopy and illite crystallization indicates kaolinite contents to be a robust proxy for palaeoclimate reconstruction. Kaolinite data show alternating warm-humid and cool-humid climate conditions that are roughly consistent with the calibrated glacial-interglacial successions recognized in high-latitude eastern Australia, including the glaciations P1 (Asselian-early Sakmarian) and P2 (late Sakmarian-early Artinskian), as well as the climatic transition to glaciation P3 (Roadian). Our results indicate a comparatively cool-humid and warm-humid climate mode in low-latitude NCP during glacial and interglacial periods, and this is a significant step toward connecting climate change in low-latitudes to high-latitude glaciation during the LPIA.

scholarly journals Large enhancements in low latitude total electron content during 15 May 2005 geomagnetic storm in Indian zone

2009 ◽  
Vol 27 (5) ◽  
pp. 1803-1820 ◽  
Author(s):  
N. Dashora ◽  
S. Sharma ◽  
R. S. Dabas ◽  
S. Alex ◽  
R. Pandey
Keyword(s):  
Solar Wind ◽  
Electric Field ◽  
Geomagnetic Storm ◽  
High Latitude ◽  
Electron Content ◽  
Low Latitude ◽  
Total Electron ◽  
H Index ◽  
The Mean ◽  
Low Latitude Ionosphere

Abstract. Results pertaining to the response of the equatorial and low latitude ionosphere to a major geomagnetic storm that occurred on 15 May 2005 are presented. These results are also the first from the Indian zone in terms of (i) GPS derived total electron content (TEC) variations following the storm (ii) Local low latitude electrodynamics response to penetration of high latitude convection electric field (iii) effect of storm induced traveling atmospheric disturbances (TAD's) on GPS-TEC in equatorial ionization anomaly (EIA) zone. Data set comprising of ionospheric TEC obtained from GPS measurements, ionograms from an EIA zone station, New Delhi (Geog. Lat. 28.42° N, Geog. Long. 77.21° E), ground based magnetometers in equatorial and low latitude stations and solar wind data obtained from Advanced Composition Explorer (ACE) has been used in the present study. GPS receivers located at Udaipur (Geog. Lat. 24.73° N, Geog. Long. 73.73° E) and Hyderabad (Geog. Lat. 17.33° N, Geog. Long. 78.47° E) have been used for wider spatial coverage in the Indian zone. Storm induced features in vertical TEC (VTEC) have been obtained comparing them with the mean VTEC of quiet days. Variations in solar wind parameters, as obtained from ACE and in the SYM-H index, indicate that the storm commenced on 15 May 2005 at 02:39 UT. The main phase of the storm commenced at 06:00 UT on 15 May with a sudden southward turning of the Z-component of interplanetary magnetic field (IMF-Bz) and subsequent decrease in SYM-H index. The dawn-to-dusk convection electric field of high latitude origin penetrated to low and equatorial latitudes simultaneously as corroborated by the magnetometer data from the Indian zone. Subsequent northward turning of the IMF-Bz, and the penetration of the dusk-to-dawn electric field over the dip equator is also discernible. Response of the low latitude ionosphere to this storm may be characterized in terms of (i) enhanced background level of VTEC as compared to the mean VTEC, (ii) peaks in VTEC and foF2 within two hours of prompt penetration of electric field and (iii) wave-like modulations in VTEC and sudden enhancement in hmF2 within 4–5 h in to the storm. These features have been explained in terms of the modified fountain effect, local low latitude electrodynamic response to penetration electric field and the TIDs, respectively. The study reveals a strong positive ionospheric storm in the Indian zone on 15 May 2005. Consequences of such major ionospheric storms on the systems that use satellite based navigation solutions in low latitude, are also discussed.

scholarly journals Equatorial electrojet as part of the global circuit: a case-study from the IEEY

1998 ◽  
Vol 16 (6) ◽  
pp. 698-710 ◽  
Author(s):  
A. T. Kobea ◽  
C. Amory-Mazaudier ◽  
J. M. Do ◽  
H. Lühr ◽  
E. Houngninou ◽  
...  
Keyword(s):  
Electric Field ◽  
Geomagnetic Storm ◽  
Electric Fields ◽  
High Latitude ◽  
Large Scale ◽  
Equatorial Electrojet ◽  
Doppler Frequency ◽  
Time Interval ◽  
Ground Field ◽  
Equatorial Latitude

Abstract. Geomagnetic storm-time variations often occur coherently at high latitude and the day-side dip equator where they affect the normal eastward Sq field. This paper presents an analysis of ground magnetic field and ionospheric electrodynamic data related to the geomagnetic storm which occured on 27 May 1993 during the International Equatorial Electrojet Year (IEEY) experiment. This storm-signature analysis on the auroral, mid-latitude and equatorial ground field and ionospheric electrodynamic data leads to the identification of a sensitive response of the equatorial electrojet (EEJ) to large-scale auroral return current: this response consists in a change of the eastward electric field during the pre-sunrise hours (0400-0600 UT) coherently to the high-, mid-, and equatorial-latitude H decrease and the disappearance of the EEJ irregularities between the time-interval 0800-0950 UT. Subsequent to the change in h'F during pre-sunrise hours, the observed foF2 increase revealed an enhancement of the equatorial ionization anomaly (EIA) caused by the high-latitude penetrating electric field. The strengthening of these irregularities attested by the Doppler frequency increase tracks the H component at the equator which undergoes a rapid increase around 0800 UT. The ∆H variations observed at the equator are the sum of the following components: SR, DP, DR, DCF and DT.Keywords. Equatorial electrojet · Magnetosphere-ionosphere interactions · Electric fields and currents · Auroral ionosphere · Ionospheric disturbances

scholarly journals Bidimensional Diagnostics, Variability, and Trends of Northern Hemisphere Blocking

2012 ◽  
Vol 25 (19) ◽  
pp. 6496-6509 ◽  
Author(s):  
Paolo Davini ◽  
Chiara Cagnazzo ◽  
Silvio Gualdi ◽  
Antonio Navarra
Keyword(s):  
Northern Hemisphere ◽  
High Latitude ◽  
Wave Breaking ◽  
Jet Stream ◽  
Low Latitude ◽  
Atlantic Sector ◽  
The Pacific ◽  
Low Latitudes ◽  
Blocking Activity ◽  
Hemisphere Winter

Abstract In this paper, Northern Hemisphere winter blocking is analyzed through the introduction of a set of new bidimensional diagnostics based on geopotential height that provide information about the occurrence, the duration, the intensity, and the wave breaking associated with the blocking. This analysis is performed with different reanalysis datasets in order to evaluate the sensitivity of the index and the diagnostics adopted. In this way, the authors are able to define a new category of blocking placed at low latitudes that is similar to midlatitude blocking in terms of the introduced diagnostics but is unable to divert or block the flow. Furthermore, over the Euro-Atlantic sector it is shown that it is possible to phenomenologically distinguish between high-latitude blocking occurring over Greenland, north of the jet stream and dominated by cyclonic wave breaking, and the traditional midlatitude blocking localized over Europe and driven by anticyclonic wave breaking. These latter events are uniformly present in a band ranging from the Azores up to Scandinavia. Interestingly, a similar distinction cannot be pointed out over the Pacific basin where the blocking activity is dominated by high-latitude blocking occurring over eastern Siberia. Finally, considering the large impact that blocking may have on the Northern Hemisphere, an analysis of the variability and the trend is carried out. This shows a significant increase of Atlantic low-latitude blocking frequency and an eastward displacement of the strongest blocking events over both the Atlantic and Pacific Oceans.

scholarly journals Spatial scale dependency of the modelled climatic response to deforestation

2012 ◽  
Vol 9 (10) ◽  
pp. 14639-14687 ◽  
Author(s):  
P. Longobardi ◽  
A. Montenegro ◽  
H. Beltrami ◽  
M. Eby
Keyword(s):  
Land Cover ◽  
Soil Carbon ◽  
Land Cover Change ◽  
Air Temperature ◽  
High Latitude ◽  
Global Climate ◽  
Surface Air Temperature ◽  
Climatic Response ◽  
Low Latitude ◽  
Low Latitudes

Abstract. Deforestation is associated with increased atmospheric CO2 and alterations to the surface energy and mass balances that can lead to local and global climate changes. Previous modelling studies show that the global surface air temperature (SAT) response to deforestation depends on latitude, with most simulations showing that high latitude deforestation results in cooling, low latitude deforestation causes warming and that the mid latitude response is mixed. These earlier conclusions are based on simulated large scale land cover change, with complete removal of trees from whole latitude bands. Using a global climate model we determine effects of removing fractions of 5% to 100% of forested areas in the high, mid and low latitudes. All high latitude deforestation scenarios reduce mean global SAT, the opposite occurring for low latitude deforestation, although a decrease in SAT is registered over low latitude deforested areas. Mid latitude SAT response is mixed. For all simulations deforested areas tend to become drier and have lower surface air temperature, although soil temperatures increase over deforested mid and low latitude grid cells. For high latitude deforestation fractions of 45% and above, larger net primary productivity, in conjunction with colder and drier conditions after deforestation, cause an increase in soil carbon large enough to generate a previously not reported net drawdown of CO2 from the atmosphere. Our results support previous indications of the importance of changes in cloud cover in the modelled temperature response to deforestation at low latitudes. They also show the complex interaction between soil carbon dynamics and climate and the role this plays on the climatic response to land cover change.

scholarly journals Latitude-dependent delay in the responses of the equatorial electrojet and <i>S</i><sub><i>q</i></sub> currents to X-class solar flares

2018 ◽  
Vol 36 (1) ◽  
pp. 139-147 ◽  
Author(s):  
Paulo A. B. Nogueira ◽  
Mangalathayil A. Abdu ◽  
Jonas R. Souza ◽  
Clezio M. Denardini ◽  
Paulo F. Barbosa Neto ◽  
...  
Keyword(s):  
Time Delay ◽  
Electric Field ◽  
Solar Flares ◽  
Extreme Ultraviolet ◽  
Equatorial Electrojet ◽  
Peak Effect ◽  
X Rays ◽  
Low Latitude ◽  
Conductivity Enhancement ◽  
Ionosphere Model

Abstract. We have analyzed low-latitude ionospheric current responses to two intense (X-class) solar flares that occurred on 13 May 2013 and 11 March 2015. Sudden intensifications, in response to solar flare radiation impulses, in the Sq and equatorial electrojet (EEJ) currents, as detected by magnetometers over equatorial and low-latitude sites in South America, are studied. In particular we show for the first time that a 5 to 8 min time delay is present in the peak effect in the EEJ, with respect that of Sq current outside the magnetic equator, in response to the flare radiation enhancement. The Sq current intensification peaks close to the flare X-ray peak, while the EEJ peak occurs 5 to 8 min later. We have used the Sheffield University Plasmasphere-Ionosphere Model at National Institute for Space Research (SUPIM-INPE) to simulate the E-region conductivity enhancement as caused by the flare enhanced solar extreme ultraviolet (EUV) and soft X-rays flux. We propose that the flare-induced enhancement in neutral wind occurring with a time delay (with respect to the flare radiation) could be responsible for a delayed zonal electric field disturbance driving the EEJ, in which the Cowling conductivity offers enhanced sensitivity to the driving zonal electric field. Keywords. Ionosphere (equatorial ionosphere)

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