Characteristics of low‐latitude Pc1 pulsations during geomagnetic storms

Bortnik, J.; Cutler, J. W.; Dunson, C.; Bleier, Thomas; McPherron, R. L.

doi:10.1029/2007ja012867

Cited by 38 publications

(51 citation statements)

References 31 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The occurrence pattern shown in Figure 10 is typical of the patterns seen in earlier studies [ Wentworth , 1964; Engebretson et al , 2008; Bortnik et al , 2008]; few, if any, events were observed during main and early recovery phases (e.g., 14–15 April), but an increasing number occurred during the middle and late recovery phases (e.g., 16–21 April). No wave events were observed either at ST5 or at Halley during the main phase day and first recovery day of the storms that began 9 April (minimum Dst = −80), 14 April (minimum Dst = −111), or 4 May (minimum Dst = −62).…”

Section: Relation To Magnetic Stormssupporting

confidence: 76%

Temporal and spatial characteristics of Pc1 waves observed by ST5

et al. 2008

View full text Add to dashboard Cite

[1] We present the results of a study of Pc1 waves (0.2-5 Hz) recorded by the three spacecraft of NASA's Space Technology 5 (ST5) mission, which operated in a dawn-dusk, 300 Â 4500 km Sun-synchronous orbit in a ''string-of-pearls'' configuration from 26 March through 23 June 2006. Regions with Pc1 wave activity are not only localized to rather narrow L shells but can appear and disappear on the time scales of $10 s to 10 min as examined by ST5. Only half of the 48 identified events were observed by all three spacecraft, and five events were observed by only one spacecraft. Only seven events were observed below L = 4, and only one was observed below L = 3.6, consistent with the relatively quiet geomagnetic conditions during this interval. The temporal occurrence distribution of Pc1 events was similar to that recorded at Halley, Antarctica (L = 4.56), during this same interval in that the number and intensity of events increased during magnetospheric compressions and during the recovery phase of magnetic storms, but they were reduced or absent during main phase and early recovery phase. This agreement suggests that if Pc1 events occur during main phase, their nearly universal absence in ground records cannot be ascribed to ionospheric screening effects or obscuration by irregular ULF noise generated in the ionosphere. These findings also suggest that although electromagnetic ion cyclotron waves might theoretically cause rapid depletion of radiation belt electrons during the main phase of storms, such waves cannot be assumed to occur during the main phase of all storms.

show abstract

Section: Relation To Magnetic Stormssupporting

confidence: 76%

Temporal and spatial characteristics of Pc1 waves observed by ST5

et al. 2008

View full text Add to dashboard Cite

show abstract

“…With the large southward IMF B z and large AE index, the EMIC waves preferentially occur in the dusk sector with large amplitudes [ Erlandson and Ukhorskiy , ; Halford et al , ; Usanova et al , ]. Moreover, their source region is also observed to extend to lower L shells with increasing storm intensity [ Bortnik et al , ]. Lyons and Thorne [] pointed out the anomalous resonant interactions of EMIC waves with relativistic electrons, which are able to scatter the electrons into the bounce loss cone through pitch angle scattering and thus cause precipitations into the atmosphere.…”

Section: Discussionmentioning

confidence: 99%

The effect of different solar wind parameters upon significant relativistic electron flux dropouts in the magnetosphere

Gao

Li²,

Bortnik³

et al. 2015

JGR Space Physics

View full text Add to dashboard Cite

Superposed epoch analyses were performed on 193 significant relativistic electron flux dropout events, in order to study the roles of different solar wind parameters in driving the depletion of relativistic electrons, using ~16 years of data from the POES and GOES missions, and the OMNIWEB solar wind database. We find that the solar wind dynamic pressure and interplanetary magnetic field (IMF) Bz play key roles in causing the relativistic electron flux dropouts, but also that either large solar wind dynamic pressure or strong southward IMF Bz by itself is capable of producing the significant depletion of relativistic electrons. The relativistic electron flux dropouts occur not only when the magnetopause is compressed closer to the Earth but also when the magnetopause is located very far (> ~10 RE). Importantly, our results show that in addition to the large solar wind dynamic pressure, which pushes the magnetopause inward strongly and causes the electrons to escape from the magnetosphere, relativistic electrons can also be scattered into the loss cone and precipitate into the Earth's atmosphere during periods of strong southward IMF Bz, which preferentially provides a source of free energy for electromagnetic ion cyclotron (EMIC) wave excitation. This is supported by the fact that the strongest electron precipitation into the atmosphere is found in the dusk sector, where EMIC waves are typically observed in the high‐density plasmasphere or plume and cause efficient electron precipitation down to ~1 MeV.

show abstract

“…Since it is well-known that Pc1 pulsations are associated with enhanced geomagnetic activity (Wentworth, 1964;Heacock and Kivinen, 1972;Bortnik et al, 2008), we test the possible connection between geomagnetic activity and earthquakes directly. Shown in panel (c) is the result of a superposed epoch analysis, performed as above, but using a sequence of 220 storm sudden commencements (SSC's) as the fiducial time.…”

Section: Earthquake Probabilitymentioning

confidence: 99%

“…3c is straightforward to interpret and shows important absolute trends, it is nevertheless somewhat deficient in that it obscures how Pc1 occurrence behaves compared with its typical behavior. To address this issue, we derive the relative probability of Pc1 occurrence similar to Bortnik et al (2008). First, the entire set of identified Pc1 pulsations is binned into 12 LT bins.…”

Section: Superposed Epoch Analysismentioning

confidence: 99%

“…The results do not show any noticeable enhancement in the relative occurrence probability of earthquakes associated with SSC's. We have also used an automatic algorithm to pick out 24 isolated storms directly from the D st index (Bortnik et al, 2008) and use the storm times as the fiducial times, performing the same superposed epoch analysis. The results (not shown), do not seem to show any correlation between geomagnetic storms and earthquakes.…”

Section: Earthquake Probabilitymentioning

confidence: 99%

See 1 more Smart Citation

The possible statistical relation of Pc1 pulsations to Earthquake occurrence at low latitudes

Bortnik¹,

Cutler²,

Dunson

et al. 2008

Ann. Geophys.

Self Cite

View full text Add to dashboard Cite

Abstract. We examine the association between earthquakes and Pc1 pulsations observed at a low-latitude station in Parkfield, California. The period under examination is ∼7.5 years in total, from February 1999 to July 2006, and we use an automatic identification algorithm to extract information on Pc1 pulsations from the magnetometer data. These pulsations are then statistically correlated to earthquakes from the USGS NEIC catalog within a radius of 200 km around the magnetometer, and M>3.0. Results indicate that there is an enhanced occurrence probability of Pc1 pulsations ∼5-15 days in advance of the earthquakes, during the daytime. We quantify the statistical significance and show that such an enhancement is unlikely to have occurred due to chance alone. We then examine the effect of declustering our earthquake catalog, and show that even though significance decreases, there is still a statistically significant daytime enhancement prior to the earthquakes. Finally, we select only daytime Pc1 pulsations as the fiducial time of our analysis, and show that earthquakes are ∼3-5 times more likely to occur in the week following these pulsations, than normal. Comparing these results to other events, it is preliminarily shown that the normal earthquake probability is unaffected by geomagnetic activity, or a random event sequence.

show abstract

Characteristics of low‐latitude Pc1 pulsations during geomagnetic storms

Cited by 38 publications

References 31 publications

Temporal and spatial characteristics of Pc1 waves observed by ST5

Temporal and spatial characteristics of Pc1 waves observed by ST5

The effect of different solar wind parameters upon significant relativistic electron flux dropouts in the magnetosphere

The possible statistical relation of Pc1 pulsations to Earthquake occurrence at low latitudes

Contact Info

Product

Resources

About