Dayside cosmic noise absorption at the equatorward boundary of auroral oval as observed from Maitri, Antarctica (<i>L</i> = 5; CGM 62.45°S, 55.45°E)

Behera, Jayanta Kumar; Sinha, A. K.; Vichare, Geeta; Козырева, О. В.; Rawat, Rahul; Dhar, Ajay

doi:10.1002/2016ja022418

Cited by 10 publications

(11 citation statements)

References 51 publications

(63 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…CNA peaks occur at the auroral stations close to the time of those substorms, which is consistent with earlier observations [ Jelly and Brice , ; Kavanagh et al , ]. In fact, it is fairly well established that the occurrence of a substorm on the nightside is a necessary condition for the observation of dayside CNA [ Kavanagh et al , , ; Behera et al , ].…”

Section: Discussionsupporting

confidence: 87%

Cosmic radio noise absorption in the high‐latitude ionosphere during solar wind high‐speed streams

et al. 2017

View full text Add to dashboard Cite

The effect of solar wind high‐speed streams (HSSs) on energetic particle precipitation at auroral and subauroral latitudes (L = 3.8–5.7) is studied by using cosmic noise absorption (CNA) data measured by the Finnish riometer chain during 95 HSS events occurring between 2006 and 2008. The data are divided into “long” and “short” HSS events, depending on whether the maximum solar wind speed is reached within 24 h or later after the arrival of the corotating interaction region (CIR) at the bow shock. We find that CNA is more frequent during long events and extends to subauroral latitudes, unlike during short events. CNA is observed for at least 4 days after the CIR arrival during long events, and only 3 days during short events. In addition, CNA is divided into three categories, depending on whether it is associated with local substorm activity, with ultralow frequency (ULF) wave activity, or neither of these. Substorm‐type CNA dominates in the 21–06 magnetic local time (MLT) sector, while ULF‐type CNA dominates from morning to afternoon and follows the daily SYM‐H index variations. This indicates the importance of having energetic (E > 30 keV) electrons available for interacting with the very low frequency (VLF) chorus waves, which may be modulated by ULF waves. Finally, we find a correlation between ULF‐type CNA on the dayside and substorm activity on the nightside with a 30 min delay, suggesting that substorm injections energize electrons, which then drift to the morning and dayside, where they precipitate into the ionosphere.

show abstract

Section: Discussionsupporting

confidence: 87%

Cosmic radio noise absorption in the high‐latitude ionosphere during solar wind high‐speed streams

et al. 2017

View full text Add to dashboard Cite

show abstract

“…Structureless patches confirm the occurrence of hiss, not chorus which is rare at L = 5 during afternoon hours. [ Behera et al , ] have shown that precipitation of particle at the day side can occur due to pitch angle scattering of subrelativistic electrons, especially in the prenoon sector. Nevertheless, the criteria that adopted in Behera et al [] have been followed in order to examine whether this is also a case of such day side CNA event or not.…”

Section: Discussionmentioning

confidence: 99%

“…[ Behera et al , ] have shown that precipitation of particle at the day side can occur due to pitch angle scattering of subrelativistic electrons, especially in the prenoon sector. Nevertheless, the criteria that adopted in Behera et al [] have been followed in order to examine whether this is also a case of such day side CNA event or not. There are two most important things viz., absence of westward electrojet over Maitri during substorm activity and a certain delay between the onset of substorm as observed in A L index and onset of CNA at Maitri qualify a CNA event to be called as a dayside CNA event at Maitri.…”

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Enhancement and modulation of cosmic noise absorption in the afternoon sector at subauroral location (L = 5) during the recovery phase of 17 March 2015 geomagnetic storm

et al. 2017

Self Cite

View full text Add to dashboard Cite

The present study has focused on the intense production of cosmic noise absorption (CNA) at Maitri, Antarctica (L = 5; CGM −62°S, 55°E) during the early recovery phase of the largest storm of the current solar cycle commenced on 17 March 2015 St. Patrick's Day. The enhancement of CNA during 15–18 UT(14–17 magnetic local time (MLT); MLT = UT − 1 at Maitri) was as large as the CNA enhancement occurred during the main phase of the storm. During this time the CNA pattern also exhibits oscillation in the Pc5 (2–7 mHz) range and is in simultaneity with geomagnetic pulsations in the same frequency range. We observed the amplitude of CNA pulsation is well correlated with the level of CNA production. High‐amplitude Pc5 oscillations were observed in the vicinity of auroral oval near Maitri. Absence of electromagnetic ion cyclotron (EMIC) waves is marked suggesting the possible role of VLF waves in precipitation. The reason for the intense CNA production is found to be the precipitation caused mainly by hiss‐driven subrelativistic electrons. The CNA enhancement event is located well inside the dusk plasmaspheric bulge region as suggested by Tsurutani et al. (2015). Signature of enhanced eastward electrojet at Maitri during 14–17 MLT could be an additional factor for such large CNA. In order to establish the cause and effect relationship between the geomagnetic and CNA oscillations at Maitri, transfer entropy method has been used, which confirmed the modulation of CNA by geomagnetic pulsations.

show abstract

“…Further, such a decrease is not seen for electron fluxes in the energy range of 40–475 keV (Figures a and b). It is believed that the keV‐range electrons are generally precipitated by very low frequency (VLF) waves or chorus emissions (Behera et al, , ). A large decrease in the flux of these electrons between 8.5 and 10 UT was seen by both GOES‐13 and GOES‐15, and this decrease might be linked to VLF/chorus wave activity.…”

Section: Particle Loss During Emic Wave Activitymentioning

confidence: 99%

Modulation of Electromagnetic Ion Cyclotron Waves by Pc5 ULF Waves and Energetic Ring Current Ions

Kakad

Omura

et al. 2019

JGR Space Physics

Self Cite

View full text Add to dashboard Cite

We present a ground observation of modulations of strong electromagnetic ion cyclotron (EMIC) waves by short and long periodicities at Indian Antarctic station, Maitri. The signatures of these waves were evident in the magnetic field variations recorded by an induction coil magnetometer during the interval 4.7-7.2 UT on 17 September 2011, a moderately disturbed day. These waves were preceded by a gradual increase in the solar wind dynamic pressure, which started at 3.88 UT. The discrete rising tone EMIC waves were observed in the Pc1 frequency band (∼0.5-0.9 Hz). The investigation of the periodicities of the observed wave spectrogram shows the presence of short (≈2.4 min) and long (≈39-69 min) periodicities. Our analysis shows that the short periodicities are associated with the Pc5 Ultra Low Frequency (ULF) waves generated by magnetic field line oscillations, while long periodicities might be associated with the ring current drifting ions. A new method, based on the cross-correlation technique, is adopted to determine sweep rates of the discrete rising tones. The average sweep rates estimated in the range of 0.44-1.9 mHz/s are relatively low as compared to the past reports of sweep rates derived from the satellite observations of EMIC waves. We found that the higher sweep rates are associated with the stronger EMIC waves on the ground, which is in agreement with the theoretical studies. This suggests that the theoretically proposed dependence of sweep rate on strength of EMIC wave in the generation region is retained even during the propagation of these waves to the ground.

show abstract

Dayside cosmic noise absorption at the equatorward boundary of auroral oval as observed from Maitri, Antarctica (L = 5; CGM 62.45°S, 55.45°E)

Cited by 10 publications

References 51 publications

Cosmic radio noise absorption in the high‐latitude ionosphere during solar wind high‐speed streams

Cosmic radio noise absorption in the high‐latitude ionosphere during solar wind high‐speed streams

Enhancement and modulation of cosmic noise absorption in the afternoon sector at subauroral location (L = 5) during the recovery phase of 17 March 2015 geomagnetic storm

Modulation of Electromagnetic Ion Cyclotron Waves by Pc5 ULF Waves and Energetic Ring Current Ions

Contact Info

Product

Resources

About