scholarly journals Topside equatorial zonal ion velocities measured by C/NOFS during rising solar activity

2014 ◽  
Vol 32 (2) ◽  
pp. 69-75 ◽  
Author(s):  
W. R. Coley ◽  
R. A. Stoneback ◽  
R. A. Heelis ◽  
M. R. Hairston
Keyword(s):  
Solar Activity ◽  
Local Time ◽  
Geomagnetic Field ◽  
General Pattern ◽  
Magnetic Latitude ◽  
Ion Drifts ◽  
F Region ◽  
Westerly Flow ◽  
Solar Local Time ◽  
Ion Velocity

Abstract. The Ion Velocity Meter (IVM), a part of the Coupled Ion Neutral Dynamic Investigation (CINDI) instrument package on the Communication/Navigation Outage Forecast System (C/NOFS) spacecraft, has made over 5 yr of in situ measurements of plasma temperatures, composition, densities, and velocities in the 400–850 km altitude range of the equatorial ionosphere. These measured ion velocities are then transformed into a coordinate system with components parallel and perpendicular to the geomagnetic field allowing us to examine the zonal (horizontal and perpendicular to the geomagnetic field) component of plasma motion over the 2009–2012 interval. The general pattern of local time variation of the equatorial zonal ion velocity is well established as westward during the day and eastward during the night, with the larger nighttime velocities leading to a net ionospheric superrotation. Since the C/NOFS launch in April 2008, F10.7 cm radio fluxes have gradually increased from around 70 sfu to levels in the 130–150 sfu range. The comprehensive coverage of C/NOFS over the low-latitude ionosphere allows us to examine variations of the topside zonal ion velocity over a wide level of solar activity as well as the dependence of the zonal velocity on apex altitude (magnetic latitude), longitude, and solar local time. It was found that the zonal ion drifts show longitude dependence with the largest net eastward values in the American sector. The pre-midnight zonal drifts show definite solar activity (F10.7) dependence. The daytime drifts have a lower dependence on F10.7. The apex altitude (magnetic latitude) variations indicate a more westerly flow at higher altitudes. There is often a net topside subrotation at low F10.7 levels, perhaps indicative of a suppressed F region dynamo due to low field line-integrated conductivity and a low F region altitude at solar minimum.

scholarly journals MODEL EMPIRIS HARI TENANG VARIASI MEDAN GEOMAGNET DI STASIUN GEOMAGNET TONDANO MANADO

2016 ◽  
Vol 12 (2) ◽  
pp. 115
Author(s):  
Lukman Arifin ◽  
John Maspupu
Keyword(s):  
Solar Activity ◽  
Local Time ◽  
Empirical Model ◽  
Geomagnetic Field ◽  
Daily Variation ◽  
Geomagnetic Disturbance ◽  
Time Interval ◽  
Field Variation ◽  
Geomagnetic Field Variation ◽  
Expression Form

Penentuan model empiris hari tenang variasi medan geomagnet dikonstruksi berdasarkan data geomagnet dari stasiun geomagnet (SG) Badan Meteorologi Klimatologi dan Geofisika (BMKG) Tondano, Manado. Hari tenang variasi medan geomagnet dinyatakan sebagai fungsi dari keempat komponen atau variabel yang mempengaruhinya yaitu: aktivitas matahari SA (solar activity), hari dalam setahun DOY (date of year), usia bulan LA (lunar age) dan waktu lokal LT (local time). Dalam bentuk matematis ditulis sebagai, EMQD ( SA, DOY, LA, LT ) = f(SA). g(DOY). h(LA). m(LT). Model empiris yang didasarkan pada fungsi kecocokan ini terdiri dari 270 bentuk ekspresi matematik. Sedangkan bentuk-bentuk ekspresi matematik ini juga mencakup proses-proses non-linier yang tak dapat diabaikan dalam model empiris hari tenang variasi medan geomagnet tersebut. Model empiris ini dapat ditiru atau dikonstruksi kembali pada suatu selang waktu yang relatif panjang (misalnya satu siklus matahari), asalkan kondisi geomagnet selalu berada dalam keadaan tenang. Kontribusi dari model empiris hari tenang ini akan memberikan informasi tentang gangguan geomagnet yang ada di stasiun geomagnet Tondano (Nilai Gangguan geomagnet = Nilai variasi medan geomagnet yang terukur – Nilai model empiris hari tenang). Dengan demikian model ini akan memberikan informasi gangguan geomagnet untuk operasi survey geomagnet disekitar stasiun geomagnet Tondano, Manado. Kata kunci : Model empiris, Hari tenang, Variasi medan geomagnet. The determination an empirical model of the quiet daily geomagnetic field variation that is constructed based on geomagnetic data from Tondano, Manado station geomagnetic This quiet daily of geomagnetic field variation was described as a function of four variables that its influence, these are solar activity (SA), day of year (DOY), lunar age (LA) and local time (LT). In the mathematically writes: EMQD ( SA, DOY, LA, LT ) = f(SA). g(DOY). h(LA). m(LT). The empirical model based on this fitting function consist of 270 coefficients which included in expression form of mathematic. While, expression form of this mathematic also comprise nonlinear processes which can not minimized in the empirical model of the quiet daily geomagnetic field variation. This empirical model can be reconstructed on the time interval that is long relative (for example one solar cycle). Provided that, under geomagnetic quiet conditions. Contribution of this empirical model of the quiet daily variation is can give information about the existence of geomagnetic disturbance at Tondano (value of geomagnetic disturbance equal value of measurable geomagnetic field variation minus value of empirical model of the quiet daily variation). Thus, information about the existence of this geomagnetic disturbance very useful for necessity geomagnetic survey at Tondano, Manado geomagnetic station. Keywords: Empirical model, the quiet daily variation, geomagnetic field variation.

scholarly journals Identifying equatorial ionospheric irregularities using in situ ion drifts

2014 ◽  
Vol 32 (4) ◽  
pp. 421-429 ◽  
Author(s):  
R. A. Stoneback ◽  
R. A. Heelis
Keyword(s):  
Solar Activity ◽  
Local Time ◽  
Density Perturbation ◽  
Equatorial Ionosphere ◽  
Morlet Wavelet ◽  
Ionospheric Irregularity ◽  
Activity Levels ◽  
Late Night ◽  
Ion Drifts

Abstract. Previous climatological investigations of ionospheric irregularity occurrence in the equatorial ionosphere have utilized in situ measurements of plasma density to identify the presence of an irregularity. Here we use the Morlet wavelet and C/NOFS to isolate perturbations in meridional ion drifts and generate irregularity occurrence maps as a function of local time, longitude, season, and solar activity. For the low solar activity levels in 2008, the distributions identified by velocity perturbations follow normalized density perturbation (ΔN/N) maps with large occurrences after midnight into dawn over all longitudes. The velocity and normalized density occurrence maps contract in both local time and longitude with increasing solar activity. By 2011 irregularities are confined to particular longitudes expected by alignment and a few hours of local time after sunset. The variation in the occurrence of the late night irregularities with solar activity is consistent with the presence of gravity wave seeding.

scholarly journals Radar and satellite investigations of equatorial evening vertical drifts and spread <i>F</i>

2015 ◽  
Vol 33 (11) ◽  
pp. 1403-1412 ◽  
Author(s):  
J. M. Smith ◽  
F. S. Rodrigues ◽  
E. R. de Paula
Keyword(s):  
Local Time ◽  
Empirical Model ◽  
Sufficient Condition ◽  
Satellite Measurements ◽  
Equatorial Spread F ◽  
Annual Variability ◽  
F Region ◽  
Plasma Drifts ◽  
Spread F ◽  
Coherent Backscatter

Abstract. We analyzed pre-midnight equatorial F region observations made by the 30 MHz coherent backscatter radar of São Luis, Brazil between August 2010 and February 2012. These measurements were processed, and used to create monthly maps of the echo occurrence as a function of local time and height. The maps show the inter-annual variability associated with equatorial spread F (ESF) occurrence in the Brazilian longitude sector. We also constructed monthly curves of the evening vertical drifts, for the Brazilian sector, using measurements by the ion velocity meter (IVM) onboard the C/NOFS satellite. The IVM evening drifts show a good overall agreement with the Scherliess and Fejer (1999) empirical model. Measured and model drifts show the development of the pre-reversal enhancement (PRE) of the vertical plasma drifts during ESF season. Using joint radar and satellite measurements, we found that evening (18:00–18:30 LT) mean non-negative drifts provide a necessary but not sufficient condition for the occurrence of topside ESF echoes. Evening downward (negative) drifts preceded the absence of topside ESF irregularities.

scholarly journals Observations of diverging field-aligned ion flow with the ESR

2004 ◽  
Vol 22 (3) ◽  
pp. 889-899 ◽  
Author(s):  
S. C. Buchert ◽  
Y. Ogawa ◽  
R. Fujii ◽  
A. P. van Eyken
Keyword(s):  
Field Line ◽  
Geomagnetic Field ◽  
Plasma Temperature ◽  
Ionization Mechanism ◽  
Soft Particle ◽  
Polar Ionosphere ◽  
Ion Composition ◽  
Ion Flow ◽  
F Region ◽  
Ionization Balance

Abstract. We report on observations of a diverging ion flow along the geomagnetic field that is often seen at the EISCAT Svalbard radar. The flow is upward above the peak of the electron density in the F-region and downward below the peak. We estimate that in such events mass transport along the field line is important for the ionization balance, and that the shape of the F-layer and its ion composition should be strongly influenced by it. Diverging flow typically occurs when there are signatures of direct entry of sheath plasma to the ionosphere in the form of intense soft particle precipitation, and we suggest that it is caused by the ionization and ionospheric electron heating associated with this precipitation. On average, 30% of all events with ion upflow also show significant ion downflow below. Key words.Ionosphere (polar ionosphere; ionization mechanism; plasma temperature and density)

scholarly journals An early mid-latitude aurora observed by Rozier (Béziers, 1780)

2020 ◽  
Vol 38 (6) ◽  
pp. 1139-1147
Author(s):  
Chiara Bertolin ◽  
Fernando Domínguez-Castro ◽  
Lavinia de Ferri
Keyword(s):  
Solar Activity ◽  
Geomagnetic Field ◽  
18Th Century ◽  
Geomagnetic Latitude ◽  
Careful Analysis ◽  
Universal Time ◽  
Low Latitudes ◽  
Solar Storms ◽  
Mass Ejection ◽  
Atmospheric Phenomena

Abstract. Aurora observations are an uncommon phenomenon at low and mid latitudes that, at the end of the 18th century, were not well known and understood. Low and mid geomagnetic latitude aurora observations provide information about episodes of intense solar storms associated with flares and outstanding coronal mass ejection (CME) and about the variation of the geomagnetic field. However, for many observers at mid and low latitudes, the features of a northern light were unknown, so they could easily report it as a phenomenon without explanation. In this work, we found that an earlier mid geomagnetic latitude aurora was observed in Beauséjour, close to Béziers (43∘19′ N, 3∘13′ E), France, by the abbot François Rozier. He was a meticulous botanist, doctor and agronomist with a special interest in atmospheric phenomena. On 15 August 1780, from 19:55 to 20:07 (Universal Time), François Rozier observed a “phosphoric cloud”. A careful analysis of the report indicates that he was reporting an auroral event. The recovery of auroral events at low and mid latitude during the 1780s is very useful for shedding light on solar activity during this period because there are few records of sunspot observations.

Possible Influence of the Solar Eclipse on the Global Geomagnetic Field

2017 ◽  
Vol 13 (S335) ◽  
pp. 167-170
Author(s):  
Jung-Hee Kim ◽  
Heon-Young Chang
Keyword(s):  
Solar Activity ◽  
Solar Cycle ◽  
Solar Eclipse ◽  
Geomagnetic Field ◽  
Geomagnetic Observatory ◽  
Geomagnetic Disturbances ◽  
Solar Eclipses ◽  
A Site

AbstractWe investigate the geomagnetic field variations recorded by INTERMAGNET geomagnetic observatories. We confirm that the effect of solar eclipse can be seen over an interval of 180 minutes centered at the time of maximum eclipse on a site of a geomagnetic observatory. It is found that the effect of the solar eclipse on the geomagnetic field becomes conspicuous as the magnitude of a solar eclipse becomes larger. The effect of solar eclipses is more evident in the second half of the path of Moon’s shadow. We also find that the effect can be overwhelmed, more sensitively by geomagnetic disturbances than by solar activity of solar cycle.

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