Electrostatic solitary wave

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In space physics, an electrostatic solitary wave (ESW) is a type of electromagnetic soliton occurring during short time scales (when compared to the general time scales of variations in the average electric field) in plasma. When a rapid change occurs in the electric field in a direction parallel to the orientation of the magnetic field, and this perturbation is caused by a unipolar or dipolar electric potential, it is classified as an ESW. [1]

Contents

Since the creation of ESWs is largely associated with turbulent fluid interactions, [2] some experiments use them to compare how chaotic a measured plasma's mixing is. [3] As such, many studies which involve ESWs are centered around turbulence, chaos, instabilities, and magnetic reconnection. [4] [5] [6] [7]

History

The discovery of solitary waves in general is attributed to John Scott Russell in 1834, [8] with their first mathematical conceptualization being finalized in 1871 by Joseph Boussinesq [9] (and later refined and popularized by Lord Rayleigh in 1876 [10] ). However, these observations and solutions were for oscillations of a physical medium (usually water), and not describing the behavior of non-particle waves (including electromagnetic waves). For solitary waves outside of media, which ESWs are classified as a , the first major framework was likely developed by Louis de Broglie in 1927, [11] though his work on the subject was temporarily abandoned and was not completed until the 1950s.

Electrostatic structures were first observed near Earth's polar cusp by Donald Gurnett and Louis A. Frank using data from the Hawkeye 1 satellite in 1978. [12] However, it is Michael Temerin, William Lotko, Forrest Mozer, and Keith Cerny b who are credited with the first observation of electrostatic solitary waves in Earth's magnetosphere in 1982. [13] Since then, a wide variety of magnetospheric satellites have observed and documented ESWs, allowing for analysis of them and the surrounding plasma conditions. [14] [15] [16]

Detection

Electrostatic solitary waves, by their nature, are a phenomenon occurring in the electric field of a plasma. As such, ESWs are technically detectable by any instrument that can measure changes to the electric field during a sufficiently short time window. However, since a given plasma's electric field can vary widely depending on the properties of the plasma and since ESWs occur in short time windows, detection of ESWs can require additional screening of the data in addition to the measurement of the electric field itself. One solution to this obstacle for detecting ESWs, implemented by NASA's Magnetospheric Multiscale Mission (MMS), is to use a digital signal processor to analyze the electric field data and isolate short-duration spikes as a candidate for an ESW. [17] Though the following detection algorithm is specific to MMS, other ESW-detecting algorithms function on similar principles. [15] [18] [19] [20]

To detect an ESW, the data from a device measuring the electric field is sent to the digital signal processor. This data is analyzed across a short time window (in the case of MMS, 1 millisecond), taking both the average electric field magnitude and the largest electric field magnitude during that time window. If the peak field strength exceeds some multiple of the average field strength (4 times the field strength in MMS), then the time window is considered to contain an ESW. [17] After this occurs, the ESW can be associated with the peak electric field strength and categorized accordingly. These algorithms vary in success at detection, since both the time window and detection multiplier are chosen by scientists based on the parameters they wish to detect. As such, these algorithms often have false positives and false negatives. [17]

Interactions

One of the primary physical consequences of ESWs is their creation of electron phase-space holes, a type of structure which prevents low velocity electrons from remaining close to the source of the ESW. [21] These phase-space holes, like the ESWs themselves, can travel stably through the surrounding plasma. Since most plasmas are overall electrically neutral, these phase-space holes often end up behaving as a positive pseudoparticle. [1]

In general, in order to form an electron phase-space hole, the electric potential energy associated with the ESW's potential needs to exceed the kinetic energy of electrons in the plasma (behavior analogous to potential hills). Research has shown that one possible set of situations where this occurs naturally are kinetic instabilities. [2] One observed example of this is the increased occurrence of these holes near Earth's bow shock and magnetopause, where the incoming solar wind collides with Earth's magnetosphere to produce large amounts of turbulence in the plasma. [22]

Forms

The definition of an ESW is broad enough that, on occasion, research distinguishes between different types:

See also

Notes

a. ^ An ESW itself is strictly an electromagnetic phenomenon, and as such is technically non-dependent on media. However, this technicality should be observed with caution. Nearly all conditions that give rise to an ESW are theorized to be dependent on the plasma medium they reside in.
b. ^ Though the identity of the other 3 co-authors is known for certain, the career of K. Cerny after the publishing of their paper is poorly documented. The first name, date, school, and major associated with graduation heavily suggest that Keith Cerny is the K. Cerny credited on the paper, but this is (as-of-yet) unconfirmed.

Related Research Articles

<span class="mw-page-title-main">Magnetopause</span> Abrupt boundary between a magnetosphere and the surrounding plasma

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<span class="mw-page-title-main">Solar wind</span> Stream of charged particles from the Sun

The solar wind is a stream of charged particles released from the Sun's outermost atmospheric layer, the corona. This plasma mostly consists of electrons, protons and alpha particles with kinetic energy between 0.5 and 10 keV. The composition of the solar wind plasma also includes a mixture of particle species found in the solar plasma: trace amounts of heavy ions and atomic nuclei of elements such as carbon, nitrogen, oxygen, neon, magnesium, silicon, sulfur, and iron. There are also rarer traces of some other nuclei and isotopes such as phosphorus, titanium, chromium, and nickel's isotopes 58Ni, 60Ni, and 62Ni. Superimposed with the solar-wind plasma is the interplanetary magnetic field. The solar wind varies in density, temperature and speed over time and over solar latitude and longitude. Its particles can escape the Sun's gravity because of their high energy resulting from the high temperature of the corona, which in turn is a result of the coronal magnetic field. The boundary separating the corona from the solar wind is called the Alfvén surface.

<span class="mw-page-title-main">Magnetic reconnection</span> Process in plasma physics

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Cluster II was a space mission of the European Space Agency, with NASA participation, to study the Earth's magnetosphere over the course of nearly two solar cycles. The mission was composed of four identical spacecraft flying in a tetrahedral formation. As a replacement for the original Cluster spacecraft which were lost in a launch failure in 1996, the four Cluster II spacecraft were successfully launched in pairs in July and August 2000 onboard two Soyuz-Fregat rockets from Baikonur, Kazakhstan. In February 2011, Cluster II celebrated 10 years of successful scientific operations in space. In February 2021, Cluster II celebrated 20 years of successful scientific operations in space. As of March 2023, its mission was extended until September 2024. The China National Space Administration/ESA Double Star mission operated alongside Cluster II from 2004 to 2007.

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References

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  3. ↑ Graham, D. B.; Khotyaintsev, Yu. V.; Vaivads, A.; André, M. (April 2016). "Electrostatic solitary waves and electrostatic waves at the magnetopause". Journal of Geophysical Research: Space Physics. 121 (4): 3069–3092. Bibcode:2016JGRA..121.3069G. doi:10.1002/2015JA021527. ISSN   2169-9380.
  4. ↑ Wang, R.; Vasko, I. Y.; Mozer, F. S.; Bale, S. D.; Kuzichev, I. V.; Artemyev, A. V.; Steinvall, K.; Ergun, R.; Giles, B.; Khotyaintsev, Y.; Lindqvist, P.-A.; Russell, C. T.; Strangeway, R. (July 2021). "Electrostatic Solitary Waves in the Earth's Bow Shock: Nature, Properties, Lifetimes, and Origin". Journal of Geophysical Research: Space Physics. 126 (7). arXiv: 2103.05240 . doi:10.1029/2021JA029357. ISSN   2169-9380.
  5. ↑ Omura, Y.; Matsumoto, H.; Miyake, T.; Kojima, H. (February 1996). "Electron beam instabilities as generation mechanism of electrostatic solitary waves in the magnetotail". Journal of Geophysical Research: Space Physics. 101 (A2): 2685–2697. doi:10.1029/95ja03145. ISSN   0148-0227.
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  12. ↑ Gurnett, D. A.; Frank, L. A. (April 1978). "Plasma waves in the polar cusp: Observations from Hawkeye 1". Journal of Geophysical Research: Space Physics. 83 (A4): 1447–1462. Bibcode:1978JGR....83.1447G. doi:10.1029/JA083iA04p01447. ISSN   0148-0227.
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  14. ↑ Graham, D. B.; Khotyaintsev, Yu. V.; Vaivads, A.; André, M. (April 2016). "Electrostatic solitary waves and electrostatic waves at the magnetopause". Journal of Geophysical Research: Space Physics. 121 (4): 3069–3092. Bibcode:2016JGRA..121.3069G. doi:10.1002/2015JA021527. ISSN   2169-9380.
  15. 1 2 Matsumoto, H.; Kojima, H.; Miyatake, T.; Omura, Y.; Okada, M.; Nagano, I.; Tsutsui, M. (1994-12-15). "Electrostatic solitary waves (ESW) in the magnetotail: BEN wave forms observed by GEOTAIL". Geophysical Research Letters. 21 (25): 2915–2918. doi:10.1029/94GL01284. ISSN   0094-8276.
  16. ↑ Fu, H. S.; Chen, F.; Chen, Z. Z.; Xu, Y.; Wang, Z.; Liu, Y. Y.; Liu, C. M.; Khotyaintsev, Y. V.; Ergun, R. E.; Giles, B. L.; Burch, J. L. (2020-03-03). "First Measurements of Electrons and Waves inside an Electrostatic Solitary Wave". Physical Review Letters. 124 (9): 095101. doi:10.1103/PhysRevLett.124.095101. ISSN   0031-9007. PMID   32202894.
  17. 1 2 3 Ergun, R. E.; Tucker, S.; Westfall, J.; Goodrich, K. A.; Malaspina, D. M.; Summers, D.; Wallace, J.; Karlsson, M.; Mack, J.; Brennan, N.; Pyke, B.; Withnell, P.; Torbert, R.; Macri, J.; Rau, D. (December 2, 2014). "The Axial Double Probe and Fields Signal Processing for the MMS Mission". Space Science Reviews. 199 (1–4): 167–188. doi: 10.1007/s11214-014-0115-x . ISSN   0038-6308.
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  19. ↑ Gurnett, D. A.; Huff, R. L.; Kirchner, D. L. (1997), Escoubet, C. P.; Russell, C. T.; Schmidt, R. (eds.), "The Wide-Band Plasma Wave Investigation", The Cluster and Phoenix Missions, Dordrecht: Springer Netherlands, pp. 195–208, doi:10.1007/978-94-011-5666-0_8, ISBN   978-94-010-6389-0 , retrieved 2024-11-06
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  21. ↑ Muschietti, L.; Ergun, R. E.; Roth, I.; Carlson, C. W. (1999-04-15). "Phase-space electron holes along magnetic field lines". Geophysical Research Letters. 26 (8): 1093–1096. Bibcode:1999GeoRL..26.1093M. doi:10.1029/1999GL900207. ISSN   0094-8276.
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  23. ↑ Ikezi, H. (1973-10-01). "Experiments on ion-acoustic solitary waves". The Physics of Fluids. 16 (10): 1668–1675. doi:10.1063/1.1694194. ISSN   0031-9171.
  24. ↑ Lakhina, Gurbax Singh; Singh, Satyavir; Rubia, Rajith; Devanandhan, Selvaraj (2021-10-21). "Electrostatic Solitary Structures in Space Plasmas: Soliton Perspective". Plasma. 4 (4): 681–731. doi: 10.3390/plasma4040035 . ISSN   2571-6182.
  25. ↑ Varghese, Steffy Sara; Singh, Kuldeep; Kourakis, Ioannis (2024-06-01). "Electrostatic supersolitary waves: A challenging paradigm in nonlinear plasma science and beyond – State of the art and overview of recent results". Fundamental Plasma Physics. 10: 100048. doi: 10.1016/j.fpp.2024.100048 . ISSN   2772-8285.
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