Evidence for particle injection as the cause of Dst reduction during HILDCAA events

Søraas, F.; Aarsnes, K.; Oksavik, K.; Sandanger, Marit Irene; Evans, David S.; Greer, Mason

doi:10.1016/j.jastp.2003.05.001

Cited by 64 publications

(53 citation statements)

References 22 publications

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“…This result may indicate moderate and irregular (possibly nonlinear) ring current responses to southward IMF Bz throughout the "recovery" of the CIR storms or HSS proper. Soraas et al (2004) observed sporadic night-side particle injection into outer shells L > 4 during HSS events. No injection to deeper shells was observed.…”

Section: Discussionmentioning

confidence: 90%

Variability of ionospheric TEC during solar and geomagnetic minima (2008 and 2009): external high speed stream drivers

et al. 2013

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We study solar wind–ionosphere coupling through the late declining phase/solar minimum and geomagnetic minimum phases during the last solar cycle (SC23) – 2008 and 2009. This interval was characterized by sequences of high-speed solar wind streams (HSSs). The concomitant geomagnetic response was moderate geomagnetic storms and high-intensity, long-duration continuous auroral activity (HILDCAA) events. The JPL Global Ionospheric Map (GIM) software and the GPS total electron content (TEC) database were used to calculate the vertical TEC (VTEC) and estimate daily averaged values in separate latitude and local time ranges. Our results show distinct low- and mid-latitude VTEC responses to HSSs during this interval, with the low-latitude daytime daily averaged values increasing by up to 33 TECU (annual average of ~20 TECU) near local noon (12:00 to 14:00 LT) in 2008. In 2009 during the minimum geomagnetic activity (MGA) interval, the response to HSSs was a maximum of ~30 TECU increases with a slightly lower average value than in 2008. There was a weak nighttime ionospheric response to the HSSs. A well-studied solar cycle declining phase interval, 10–22 October 2003, was analyzed for comparative purposes, with daytime low-latitude VTEC peak values of up to ~58 TECU (event average of ~55 TECU). The ionospheric VTEC changes during 2008–2009 were similar but ~60% less intense on average. There is an evidence of correlations of filtered daily averaged VTEC data with Ap index and solar wind speed. We use the infrared NO and CO2 emission data obtained with SABER on TIMED as a proxy for the radiation balance of the thermosphere. It is shown that infrared emissions increase during HSS events possibly due to increased energy input into the auroral region associated with HILDCAAs. The 2008–2009 HSS intervals were ~85% less intense than the 2003 early declining phase event, with annual averages of daily infrared NO emission power of ~ 3.3 × 1010 W and 2.7 × 1010 W in 2008 and 2009, respectively. The roles of disturbance dynamos caused by high-latitude winds (due to particle precipitation and Joule heating in the auroral zones) and of prompt penetrating electric fields (PPEFs) in the solar wind–ionosphere coupling during these intervals are discussed. A correlation between geoeffective interplanetary electric field components and HSS intervals is shown. Both PPEF and disturbance dynamo mechanisms could play important roles in solar wind–ionosphere coupling during prolonged (up to days) external driving within HILDCAA intervals

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Section: Discussionmentioning

confidence: 90%

Variability of ionospheric TEC during solar and geomagnetic minima (2008 and 2009): external high speed stream drivers

et al. 2013

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“…The bottom panel shows the Dst index, which increased slowly from −40 to −20 nT. Particle precipitation in the ring current during the HILDCAA event can be responsible for the slow variations of the Dst index (Soraas et al, 2004).…”

Section: Resultsmentioning

confidence: 99%

“…The long duration of the recovery phase of the geomagnetic storms followed by HILDCAAs (Tsurutani and Gonzalez, 1987) was explained by Soraas et al (2004) as being due to precipitation of particles in the ring current during HILDCAA events. Such particle precipitation prevents the decay of the ring current, which delays the Dst (disturbance storm time) recovery.…”

Section: Introductionmentioning

confidence: 99%

Cross-correlation and cross-wavelet analyses of the solar wind IMF B_z and auroral electrojet index AE coupling during HILDCAAs

Souza

Echer

Bolzan³

et al. 2018

Ann. Geophys.

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Abstract. Solar-wind-geomagnetic activity coupling during high-intensity long-duration continuous AE (auroral electrojet) activities (HILDCAAs) is investigated in this work. The 1 min AE index and the interplanetary magnetic field (IMF) B z component in the geocentric solar magnetospheric (GSM) coordinate system were used in this study. We have considered HILDCAA events occurring between 1995 and 2011. Cross-wavelet and cross-correlation analyses results show that the coupling between the solar wind and the magnetosphere during HILDCAAs occurs mainly in the period ≤ 8 h. These periods are similar to the periods observed in the interplanetary Alfvén waves embedded in the high-speed solar wind streams (HSSs). This result is consistent with the fact that most of the HILDCAA events under present study are related to HSSs. Furthermore, the classical correlation analysis indicates that the correlation between IMF B z and AE may be classified as moderate (0.4-0.7) and that more than 80 % of the HILDCAAs exhibit a lag of 20-30 min between IMF B z and AE. This result corroborates with Tsurutani et al. (1990) where the lag was found to be close to 20-25 min. These results enable us to conclude that the main mechanism for solar-wind-magnetosphere coupling during HILDCAAs is the magnetic reconnection between the fluctuating, negative component of IMF B z and Earth's magnetopause fields at periods lower than 8 h and with a lag of about 20-30 min.

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“…These differences, although rather small for conclusive evidence, may still be indicative of a systematic long-term change in the interplanetary conditions. The weaker main phase and the longer recovery phase in the early period suggests that the storms at that time were more typically driven by recurrent streams (often producing HILDCAA, high intensity long duration continuous AE activity, type storm recovery phases (Tsurutani and Gonzales, 1987;Søraas et al, 2004)), rather than by strong CMEs, as typical in more recent times.…”

Section: Superposed Epoch Analysis Of Geomagnetic Stormsmentioning

confidence: 97%

A new reconstruction of the Dst index for 1932-2002

Karinen

Мурсула

2005

Ann. Geophys.

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Abstract. We have reconstructed a new, homogeneous geomagnetic D st index for , thus extending the original D st index by 25 years, i.e. by more than one full solar magnetic cycle. The extension was done by using data from the original set of four low-latitude stations for [1941][1942][1943][1944][1945][1946][1947][1948][1949][1950][1951][1952][1953][1954][1955][1956], and by using the nearby CTO station as a predecessor of the HER station for [1932][1933][1934][1935][1936][1937][1938][1939][1940]. Despite some open questions related to the composition of the original D st index, the reconstructed index is quite similar to the original one during the overlapping time interval . However, the reconstructed D st index corrects for some known errors in the original D st index, such as the erroneously large daily UT variation in 1971. Also, despite the overall agreement, the reconstructed index deviates from the original index even on the level of annual averages for several years. For instance, all annual averages of the reconstructed index are negative, and for 1962-1966 they are systematically lower (more stormy) than those of the original index. Accordingly, we disagree with the uniquely positive annual average of the original index in 1965, which most likely is erroneous. We also find somewhat higher (less stormy) values than in the original D st index for the three lowest annual averages in 1960, 1989 and 1991, out of which the lowest annual average is found in 1989 rather than in 1991. The annual averages of the geomagnetic A p index and the reconstructed D st index correlate very well over this time interval, except in the beginning of the series in 1932-1940 and in the declining phase of solar cycles 18, 20 and 21, where high speed solar wind streams cause enhanced geomagnetic activity. Using the superposed epoch method we also find that, on average, the storms in the early extended period are less intense but tend to have a longer recovery phase, suggesting that there are more HILDCAA-type medium activity intervals during the early period than more recently. We also study the annually averaged storm structure over the 71-year time interval and find that the most stormy years occur during the declining phase of solar cycles 17 and 21 and around the solar maxima of cycles 19 and 22.

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Evidence for particle injection as the cause of Dst reduction during HILDCAA events

Cited by 64 publications

References 22 publications

Variability of ionospheric TEC during solar and geomagnetic minima (2008 and 2009): external high speed stream drivers

Variability of ionospheric TEC during solar and geomagnetic minima (2008 and 2009): external high speed stream drivers

Cross-correlation and cross-wavelet analyses of the solar wind IMF B_z and auroral electrojet index AE coupling during HILDCAAs

A new reconstruction of the <i>D<sub>st</sub></i> index for 1932-2002

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Evidence for particle injection as the cause of Dst reduction during HILDCAA events

Cited by 64 publications

References 22 publications

Variability of ionospheric TEC during solar and geomagnetic minima (2008 and 2009): external high speed stream drivers

Variability of ionospheric TEC during solar and geomagnetic minima (2008 and 2009): external high speed stream drivers

Cross-correlation and cross-wavelet analyses of the solar wind IMF Bz and auroral electrojet index AE coupling during HILDCAAs

A new reconstruction of the &lt;i&gt;D&lt;sub&gt;st&lt;/sub&gt;&lt;/i&gt; index for 1932-2002

Contact Info

Product

Resources

About

Cross-correlation and cross-wavelet analyses of the solar wind IMF B_z and auroral electrojet index AE coupling during HILDCAAs

A new reconstruction of the <i>D<sub>st</sub></i> index for 1932-2002