Jets Downstream of Collisionless Shocks

Plaschke, Ferdinand; Hietala, Heli; Archer, Martin; Blanco‐Cano, X.; Kajdič, Primož; Karlsson, Tomas; Lee, Sun Hee; Omidi, N.; Palmroth, Minna; Roytershteyn, V.; Schmid, Daniel; Сергеев, В. А.; Sibeck, D. G.

doi:10.1007/s11214-018-0516-3

Cited by 118 publications

(171 citation statements)

References 228 publications

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“…Our statistical investigation compares the orientation of the IMF and the fluctuations observed by GMAGs. It is suggested that during certain IMF configurations jets are more common [23], and if we can observe more variations in the GMAG observations during such configurations, this can be explained by jets. The project is meant to act as a pre-study for further investigations on a PhD level.…”

Section: Introductionmentioning

confidence: 84%

“…15), observations from GMAGs seem to fluctuate more during radial IMF. During this IMF orientation, jets are suggested to be more common [23]. To investigate if this is a general behavior, that is, GMAG observations show more fluctuations during radial IMF, we performed a statistical investigation comparing IMF orientation with GMAG observations.…”

Section: Statistical Study Of Imf Orientationmentioning

confidence: 99%

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Geoeffectiveness of Magnetosheath Jets

Norenius¹,

Hamrin²,

Goncharov³

et al. 2020

Preprint

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In this report we present spacecraft and ground-based observations of magnetosheath jets impacting the magnetosphere, both as a case study and a statistical study. In the case study, jets were detected in the magnetosheath by the Magnetospheric MultiScale mission, MMS. By utilizing a data-based magnetospheric model (Tsyganenko T96 [29]), we estimated which jets were likely to impact the magnetopause and where they would do so. We examined ground based magnetometers, GMAGs, at the expected foot-point to the affected magnetic field line and compared this with the spacecraft observations. Theoretical transfer times for a jet to be detectable by GMAGs have been estimated and compared with the observed time delay, from detection to GMAG response, and they were in good agreement for all cases. The times found for this geoeffective response were found to be around 1-2 min, and the response in the GMAGs was in the form of a pulse with an amplitude of around 50 nT. We suggest that jets of a long enough time duration can be geoeffective in a way that they are detectable at ground level by GMAGs. It was also found that GMAGs fluctuate more during periods containing many detected jets.We performed our statistical study with the intention of comparing fluctuations in GMAG observations during Interplanetary Magnetic Field, IMF, configurations which is suggested to be favorable for jet creation. The IMF observations was provided by the THEMIS (Time History of Events and Macroscale Interactions during Substorms) spacecraft. This was done by selecting periods of steady IMF with different orientations, and examining the GMAG variations. GMAGs were selected based on a region where most of our foot-points were found in our previous case study. We performed this study over a three year interval, and found that GMAGs observe about 2 nT higher variation, according to their standard deviations, during radial IMF compared to northward IMF. During northward IMF we expect less effects from magnetopause phenomena, thus making it suitable to compare with radial IMF. Our statistical investigation support our findings that magnetosheath jets can be geoeffective in a way that GMAGs can detect them.ii Acknowledgements I would like to show my appreciations to a couple of people who have helped me in various ways during my University studies and this final project. Firstly, I would like to thank my friends from the engineering physics program, if you can translate the English hockey term "grind" into Swedish, all persons concerned will know who I mean. All of you have made these last five years a some the most entertaining and I have experienced. I would also like to thank my girlfriend Felicia, for encouraging and supporting me greatly during both my studies, this project and my future plans. I also owe much gratitude to Oleksandr and Maria for incredibly valuable comments and suggestions for this project, both in regards of the physics and the writing. The entire space physics group at Umeå University have been very helpful and welcoming during ...

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Section: Introductionmentioning

confidence: 84%

Section: Statistical Study Of Imf Orientationmentioning

confidence: 99%

Geoeffectiveness of Magnetosheath Jets

Norenius¹,

Hamrin²,

Goncharov³

et al. 2020

Preprint

Self Cite

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“…What is more important, there is no reliable information on electric fields at heights of 500-2000 km, because measurements there are difficult, and, as a consequence of this, empirical electric field models are limited and do not provide the results below L ∼ 2 (e.g. Rowland and Wygant, 1998;Matsui et al, 2013). The most modern research suggests that the actual strength of penetration electric fields can be stronger than any existing electric field model at L < 2 (Su et al, 2016).…”

Section: Introductionmentioning

confidence: 99%

Energetic electron enhancements under the radiation belt (<i>L</i> < 1.2) during a non-storm interval on 1 August 2008

2019

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Abstract. An unusual event of deep injections of >30 keV electrons from the radiation belt to low L shells (L<1.2) in the midnight–dawn sector was found from NOAA/POES observations during quiet geomagnetic conditions on 1 August 2008. Using THEMIS observations in front of the bow shock, we found transient foreshock conditions and interplanetary magnetic field (IMF) discontinuities passing the subsolar region at that time. These conditions resulted in generation of plasma pressure pulses and fast plasma jets observed by THEMIS, respectively, in the foreshock and magnetosheath. Signatures of interactions of pressure pulses and jets with the magnetopause were found in THEMIS and GOES measurements in the dayside magnetosphere and ground magnetogram records from INTERMAGNET. The jets produce penetration of hot magnetosheath plasma into the dayside magnetosphere, as was observed by the THEMIS probes after approaching the magnetopause. High-latitude precipitations of the hot plasma were observed by NOAA/POES satellites on the dayside. The precipitations preceded the >30 keV electron injections at low latitudes. We propose a scenario of possible association between the phenomena observed. However, the scenario cannot be firmly supported because of the lack of experimental data on electric fields at the heights of electron injections. This should be a subject of future experiments.

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“…In addition to the global scale structure of the magnetosphere, there are various types of local spatial and temporal variations caused either by discontinuities in the solar wind or by the non-linear evolution of the system itself. Some examples of local variations include foreshock transients (e.g., Schwartz and Burgess, 1991), magnetopause surface waves (e.g., Plaschke et al, 2009) and transient structures in the magnetosheath (e.g., Plaschke et al, 2018). 20 One and the most common type of magnetosheath transients are local dynamic pressure enhancements called magnetosheath jets , and the references therein).…”

Section: Introductionmentioning

confidence: 99%

Jets in the Magnetosheath: IMF Control of Where They Occur

Vuorinen¹,

Hietala²,

Plaschke³

2019

Preprint

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Abstract. Magnetosheath jets are localized regions of plasma that move faster towards the Earth than the surrounding magnetosheath plasma. Due to their high velocities, they can cause indentations when colliding into the magnetopause and trigger processes such as magnetic reconnection and magnetopause surface waves. We statistically study the occurrence of these jets in the subsolar magnetosheath using measurements from the five Time History of Events and Macroscale Interactions during Substorms (THEMIS) spacecraft and OMNI solar wind data from 2008–2011. We present the observations in the BIMF-vSW plane and study the spatial distribution of jets during different interplanetary magnetic field (IMF) orientations. Jets occur downstream of the quasi-parallel bow shock approximately 9 times as often as downstream of the quasi-perpendicular shock, suggesting that foreshock processes are responsible for most jets. For oblique IMF, with 30°–60° cone angle, the occurrence increases monotonically from the quasi-perpendicular side to the quasi-parallel side. This study offers predictability for the numbers and locations of jets observed during different IMF orientations allowing us to better forecast the formation of these jets and their impact on the magnetosphere.

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Jets Downstream of Collisionless Shocks

Cited by 118 publications

References 228 publications

Geoeffectiveness of Magnetosheath Jets

Geoeffectiveness of Magnetosheath Jets

Energetic electron enhancements under the radiation belt (<i>L</i> < 1.2) during a non-storm interval on 1 August 2008

Jets in the Magnetosheath: IMF Control of Where They Occur

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Jets Downstream of Collisionless Shocks

Cited by 118 publications

References 228 publications

Geoeffectiveness of Magnetosheath Jets

Geoeffectiveness of Magnetosheath Jets

Energetic electron enhancements under the radiation belt (&lt;i&gt;L&lt;/i&gt; &lt; 1.2) during a non-storm interval on 1 August 2008

Jets in the Magnetosheath: IMF Control of Where They Occur

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Energetic electron enhancements under the radiation belt (<i>L</i> < 1.2) during a non-storm interval on 1 August 2008