scholarly journals Day-to-day correlation of equatorial electrojet at two stations separated by 2000 km

2007 ◽  
Vol 25 (4) ◽  
pp. 875-880 ◽  
Author(s):  
R. G. Rastogi ◽  
H. Chandra ◽  
D. Chakrabarty ◽  
K. Kitamura ◽  
K. Yumoto
Keyword(s):  
Spectral Analysis ◽  
Geomagnetic Field ◽  
Ring Current ◽  
Equatorial Electrojet ◽  
Time Effects ◽  
Mean Values ◽  
Remarkable Similarity ◽  
Dst Index ◽  
Daily Range ◽  
Dominant Period

Abstract. Day-to-day fluctuations of the daily range of the geomagnetic field H at the equatorial electrojet stations Ancon (ANC, 77.0° W) and Sao Luis (SLZ, 44.2° W) are described for the period January–June 1993. The H field started increasing between midnight and sunrise, reaching a peak shortly before noon. The daily range of H was maximum during March and April and minimum during June. Regardless of the month, the range in H was significantly larger at ANC than at SLZ. The 27-day running mean of the range of H varied from 80 nT to 125 nT at SLZ and from 105 nT to 180 nT at ANC. The day-to-day values of the range of H showed very faithful variations at the two stations. The deviations of the daily range of H from its 27-day running mean values showed good correlation between the two stations. Some large storm-time effects were seen at both stations. The correlation was still significant, when data were corrected for Dst index values. It is suggested that the range in H at the two electrojet stations, separated by more than 2000 km, are affected by some common sources other than the ring current, which need to be identified. Spectral analysis of the range of H shows remarkable similarity at the two stations, with a dominant period of 15 days at both stations.

THE STUDY OF LONGITUDINAL AND LATITUDINAL VARIATION OF EQUATORIAL ELECTROJET SIGNATURE AT STATIONS WITHIN THE 96°MM AND 210°MM AFRICAN AND ASIAN SECTORS RESPECTIVELY UNDER QUIET CONDITIONS.

2021 ◽  
Vol 5 (2) ◽  
pp. 511-532
Author(s):  
Aniefiok Akpaneno ◽  
Matthew Joshua ◽  
K. R. Ekundayo
Keyword(s):  
Seasonal Variation ◽  
Geomagnetic Field ◽  
Satellite Communication ◽  
Equatorial Electrojet ◽  
Latitudinal Variation ◽  
Magnetic Data ◽  
Horizontal Magnetic Field ◽  
Baseline Values ◽  
The Difference ◽  
Current Systems

Solar quiet current (S_q) and Equatorial Electrojet (EEJ) are two current systems which are produced by electric current in the ionosphere.  The enhancement of the horizontal magnetic field is the EEJ. This research is needed for monitoring equatorial geomagnetic current which causes atmospheric instabilities and affects high frequency and satellite communication. This study presents the longitudinal and latitudinal variation of equatorial electrojet signature at stations within the 96°mm and 210°mm African and Asian sectors respectively during quiet condition. Data from eleven observatories were used for this study. The objectives was  to determine the longitudinal and latitudinal geomagnetic field variations during solar quiet conditions, Investigate monthly variation and diurnal transient seasonal variation; Measure the strength of the EEJ at stations within the same longitudinal sectors and find out the factors responsible for the longitudinal and latitudinal variation of EEJ. Horizontal (H) component of geomagnetic field for the year 2008 from Magnetic Data Acquisition System (MAGDAS) network were used for the study. The International Quiet Days (IQDs) were used to identify quiet days. Daily baseline values for each of the geomagnetic element H  were obtained.  The monthly average of the diurnal variation was found. The seasonal variation of dH was found. Results showed that: The longitudinal and latitudinal variation in the dH differs in magnitude from one station to another within the same longitude due to the difference in the influence of the EEJ on them.

scholarly journals A Comparison of Equatorial Electrojet in Peru and East Brazil

2013 ◽  
Vol 7 (1) ◽  
pp. 29-36 ◽  
Author(s):  
R.G. Rastogi ◽  
H. Chandra ◽  
Rahul Shah ◽  
N.B. Trivedi ◽  
S.L. Fontes
Keyword(s):  
South America ◽  
Geomagnetic Field ◽  
Daily Variation ◽  
Equatorial Electrojet ◽  
Horizontal Component ◽  
Low Latitude ◽  
Vertical Field ◽  
The Mean ◽  
Western Side ◽  
The Magnetic Field

The paper describes the characteristics of the equatorial electrojet at Huancayo (HUA, 12.1oS, 75.3oW, inclination 1.5oN, declination 1.0oE) in western side of South America, where the geomagnetic field is aligned almost along the geographic meridian, and at Itinga (ITI, 4.3oS, 47.oW, inclination 1.4oN, declination 19.3oW) in eastern part of South America, where the geomagnetic field is aligned about 19o west of the geographic meridian; although the mean intensity of the magnetic field in the two regions are almost of the same order. Further comparisons are made of the current at Itinga and at Tatuoca (TTB, 1.2oS, 48.5oW, inclination 7.8o N, declination 18.7oW), a low latitude station in the same longitude sector. The daily range of horizontal component of the geomagnetic field, H, is shown to be almost 16% higher at HUA compared to that at ITI. The daily variation of the eastward field, Y, showed a strong minimum of -40 nT around 13-14 hr LT at ITI whereas very low values were observed at HUA with a positive peak of about 4 nT around 11- 12 hr LT. The vertical field, Z, showed abnormally large negative values of -70 nT at TTB around 13 hr LT. The day-today fluctuations of midday and midnight values of X field were positively correlated between HUA and ITI with a high correlation coefficient of 0.78 and 0.88 respectively. Values of Y field were also significantly positively correlated between HUA and ITI for midnight hours (0.72), while no correlation was observed for the midday hours. The midnight values of X field at HUA, ITI and TTB showed significant (0.90 or greater) correlation with Dst index. Correlation values of about 0.7 were observed between Dst and midday values of X at ITI and TTB and to a lesser degree (0.4) at HUA.

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.

INVESTIGATING THE VARIATIONS OF HORIZONTAL (H) AND VERTICAL (Z) COMPONENTS OF THE GEOMAGNETIC FIELD AT SOME EQUATORIAL ELECTROJET STATIONS

2021 ◽  
Vol 5 (1) ◽  
pp. 539-557
Author(s):  
Aniefiok Akpaneno ◽  
O. N. Abdulahi
Keyword(s):  
Seasonal Variations ◽  
High Frequency ◽  
Geomagnetic Field ◽  
Satellite Communication ◽  
Geomagnetic Latitude ◽  
Equatorial Electrojet ◽  
Geomagnetic Equator ◽  
Monthly Average ◽  
June Solstice ◽  
Baseline Values

This research is monitoring equatorial geomagnetic current which causes atmospheric instabilities and affects high frequency and satellite communication. It presents the variations of Horizontal (H) and vertical (Z) component of the geomagnetic field at some Equatorial Electrojet (EEJ) Stations during quiet days. Data from five (5) observatories along the magnetic equator were used for the study. Daily baseline values for each of the geomagnetic element 𝐻 and Z were obtained. The monthly average of the diurnal variation and the seasonal variations were found. Results showed that the variations of the geomagnetic element of both H and Z differ in magnitudes from one stations to another along the geomagnetic Equator due to the differences of their geomagnetic latitude. The Amplitude curves for Z) are seen to be conspicuously opposite to that of H), and there is absence of CEJ in Z- Component but present in H- Components. The  values during the pre-sunrise hours are low compare to daytime hours. Minimum variations of dH was observed during June solstice and maximum variations was observed during Equinox season. This study shows that daily variations of (H) and (Z) occur in all the stations. The enhancement in H is as a result of EEJ current.

scholarly journals Case studies of the propagation characteristics of auroral TIDS with EISCAT CP2 data using maximum entropy cross-spectral analysis

1998 ◽  
Vol 16 (2) ◽  
pp. 161-167 ◽  
Author(s):  
S. Y. Ma ◽  
K. Schlegel ◽  
J. S. Xu
Keyword(s):  
Spectral Analysis ◽  
Phase Velocity ◽  
Maximum Entropy ◽  
Case Studies ◽  
Large Scale ◽  
Phase Speed ◽  
Wave Number ◽  
Propagation Characteristics ◽  
Dominant Period ◽  
Horizontal Wavelength

Abstract. In this paper case studies of propagation characteristics of two TIDs are presented which are induced by atmospheric gravity waves in the auroral F-region on a magnetic quiet day. By means of maximum entropy cross-spectral analysis of EISCAT CP2 data, apparent full wave-number vectors of the TIDs are obtained as a function of height. The analysis results show that the two events considered can be classified as moderately large-scale TID and medium-scale TID, respectively. One exhibits a dominant period of about 72 min, a mean horizontal phase speed of about 180 m/s (corresponding to a horizontal wavelength of about 780 km) directed south-eastwards and a vertical phase speed of 55 m/s for a height of about 300 km. The other example shows a dominant period of 44 min, a mean horizontal phase velocity of about 160 m/s (corresponding to a horizontal wavelength of about 420 km) directed southwestwards, and a vertical phase velocity of about 50 m/s at 250 km altitude.Key words. Ionosphere · Auroral ionosphere · Ionosphere-atmosphere interactions · Wave propagation)

scholarly journals The Polar Cap (PC) index combination, PCC: relations to solar wind properties and global magnetic disturbances

2020 ◽  
Author(s):  
Peter Stauning
Keyword(s):  
Solar Wind ◽  
Energy Input ◽  
Source Function ◽  
Ring Current ◽  
Mean Deviation ◽  
Polar Cap ◽  
Geomagnetic Disturbances ◽  
The Real ◽  
Dst Index ◽  
Saturation Effects

The non-negative Polar Cap PCC index built from PCN (North) and PCS (South) correlates considerably better with the solar wind merging electric field and is more representative for the total energy input from the solar wind to the magnetosphere and for the development of geomagnetic disturbances than either of the hemispheric indices. The present work shows that the ring current index, Dst, to a high degree of accuracy can be derived from a source function built on the PCC indices. The integration of the PCC-based source function throughout the interval from 1992 to 2018 without attachment to the real Dst indices based on low latitude magnetic observations has generated equivalent Dst values that correlate very well (R=0.86) with the real Dst index values, which are represented with a mean deviation less than 1 nT and an overall rms deviation less than 13 nT. The precise correlation between the real and equivalent Dst values have been used to correct the PCC indices for saturation effects at high intensity disturbance conditions where the Dst index may take values beyond -100 nT. The relations between PCC and the ring current indices, Dst and ASY-H have been used, in addition, to derive the precise timing between polar cap convection processes reflected in the polar cap indices and the formation of the partial and total ring current systems. Building the ring current is considered to represent the energy input from the solar wind, which also powers auroral disturbance processes such as substorms and upper atmosphere heating. Thus, the PCC indices measuring accurately the energy input from the solar wind are powerful tools for space weather monitoring and for solar-terrestrial research.

scholarly journals GEOMETRIC FACTOR IN SEASONAL VARIATIONS OF DAILY AVERAGE VALUES OF THE GEOMAGNETIC INDEX Dst

2020 ◽  
Vol 6 (4) ◽  
pp. 50-56
Author(s):  
Georgy Makarov
Keyword(s):  
Seasonal Variations ◽  
Annual Variation ◽  
Ring Current ◽  
The Sun ◽  
Geomagnetic Index ◽  
Dst Index ◽  
Average Value ◽  
Daily Average ◽  
Geometric Factors ◽  
Semiannual Variation

The work uses data on the geomagnetic index Dst for the period 1966–2015. Under quiet conditions, the occurrence of seasonal variations of the daily average Dst index depends on geometric factors of the interaction between the solar wind and the magnetosphere; and under disturbed conditions, on the development of a partial ring current in the magnetosphere. At large negative values of the Dst index, there is no seasonal variation in it. The imperfection of the network of Dst stations is assumed to lead to the formation of annual variation in Dst. The formation of a semiannual variation is associated with the movement of the plasma sheet relative to the plane of the geomagnetic equator during the annual rotation of Earth around the Sun. Based on the data on semiannual variations in the number of days n(Dst), the critical daily average value of the geomagnetic index Dst is determined, starting from which we can speak of disturbed days: Dst≤–24 nT.

scholarly journals Power Spectral Analysis of Heart Rate Variability In Hypothyroidism

1970 ◽  
Vol 5 (2) ◽  
pp. 53-59 ◽  
Author(s):  
Matia Ahmed ◽  
Noorzahan Begum ◽  
Sultana Ferdousi ◽  
Shelina Begum ◽  
Taskina Ali
Keyword(s):  
Spectral Analysis ◽  
Nervous Activity ◽  
Power Spectral Analysis ◽  
Autonomic Nervous Activity ◽  
Mean Values ◽  
Power Spectral ◽  
Group A ◽  
The Mean ◽  
Hypothyroid Patients ◽  
Serum Tsh

Background: Hypothyroidism is one of the common clinical problems with high incidence in women particularly in older age. It has profound effect on metabolic processes in almost all tissue of the body and heart is particularly sensitive to thyroid hormone action. Power spectral analysis (PSA)is useful to determine the cardiac autonomic regulation by assessing sympathovagal balance. Objectives: To assess the cardiac autonomic nervous activity by power spectral analysis of heart rate variability in patients with hypothyroidism.Method: This cross sectional study was carried out in the Department of Physiology, Banghabandhu Sheikh Mujib Medical University from 1st July 2008 to 30th June 2009 on 60 female patients of 30-50 years with hypothyroidism (group B). For comparison, 30 age sex matched apparently healthy euthyroid subjects (group A) were also studied. Based on treatment, hypothyroid patients were divided into B1 (patients on their 1st day of diagnosis, before starting of treatment) and B2 (patients with medication for 12-18 months). The patients were selected from the Out Patients Department of Endocrinology, BSMMU. Serum TSH and FT4 levels of all subjects were measured by AxSYM system. To perform power spectral analysis of HRV Total Power (TP), Low Frequency (LF), High Frequency (HF), LF norms (nu), HF norms (nu) and LF/HF ratio were assessed by a Polyrite. For statistical analysis of data, Independent Sample t test, One Way ANOVA and Pearson’s correlation coefficient test were done as applicable.Results: The mean serum TSH (38.16 vs2.18; 2.04) was significantly higher and FT4 (5.12vs 15.13; 15.08) was significantly lower (p<0.001) in group B1 than those of group A and B2. The mean values of all the spectral parameters of HRV in euthyroid subjects were within normal range. In untreated hypothyroid patients the mean values of TP (77.11vs2702.87; 2683.73), HF power (56.68 vs 342.02; 437.34) HF nu (24.79 vs 36.35; 34.55) were found significantly (p<0.001) lower LF/HF (1.7±0.3,3.16±.84 and 1.93±.58) and LF nu (75.32 vs 63.71, and 65.90) were significantly (p<0.001) higher and in comparison to both euthyroids and treated patients. Conclusion: Alteration in cardiac autonomic nervous activity characterized by reduced vagal modulation and higher sympathetic activity may occur in the hypothyroid patients.Keywords: HRV; LF HF LF/HF Hypothyroidism DOI: 10.3329/jbsp.v5i2.6777J Bangladesh Soc Physiol. 2010 December; 5(2): 53-59

scholarly journals Ring current response to impulsive southward IMF: A cause of second development of the Dst index.

1990 ◽  
Vol 42 (11) ◽  
pp. 1325-1331 ◽  
Author(s):  
Shun TAKAHASHI ◽  
Toshihiko IYEMORI ◽  
Masahiko TAKEDA
Keyword(s):  
Ring Current ◽  
Current Response ◽  
Second Development ◽  
Dst Index
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