Helmet streamers, also known as coronal streamers, are elongated cusp-like structures in the Sun's corona which are often visible in white-light coronagraphs and during solar eclipses. They are closed magnetic loops which lie above divisions between regions of opposite magnetic polarity on the Sun's surface. The solar wind elongates these loops to pointed tips which can extend a solar radius or more into the corona.[1]
Helmet streamers during a total solar eclipse, photographed using exposure bracketing to show both the Sun's corona and the surface features of the new moon itself, illuminated by earthshine. A few solar prominences are visible around the lunar limb.
During solar minimum, helmet streamers are found closer to the heliographic equator, whereas during solar maximum they are found more symmetrically distributed around the Sun.
Helmet streamers appear bright in white-light relative to the surrounding coronal plasma.
Helmet streamers have cusp-like bases that taper radially outward away from the Sun forming long stalks. The base typically extends up to 1.5 solar radii above the surface, whereas the stalk—stretched outward by the solar wind—can extend over many solar radii.[2]
Helmet streamers are structured by closed magnetic fields and lie above boundaries separating opposite magnetic polarity in the Sun's photosphere. Their thin stalks consist of oppositely directed magnetic fields which form current sheets.[3] Surrounding these stalks are open, oppositely directed magnetic fields which are anchored to coronal holes lower in the corona.[4]
The white-light emissions of helmet streamers is due to the high electron density of the confined plasma relative to the surrounding corona. Light from the photosphere is Thomson scattered off of these electrons with the intensity of scattered light depending on the number of electrons along the observer's line of sight.[5]
Small blobs of plasma, or "plasmoids" are sometimes released from the tips of helmet streamers, and this is one source of the slow component of the solar wind.[1][better source needed]
Around solar minimum, the point of minimum solar activity during the 11-year solar cycle, helmet streamers are generally located around the heliographic equator in what is referred to as the streamer belt. At the same time, large coronal holes are present at the poles. As solar activity increases near the solar maximum, helmet streamers appear more symmetrically around the Sun.[3]
Solar minimum
Solar maximum
Coronagraphs taken near the solar minimum between solar cycles 22 and 23 and near the solar maximum of solar cycle 23 demonstrate the different distributions of helmet streamers around the solar disk at different points in a solar cycle.
Role in coronal mass ejectionsedit
As Parker Solar Probe passed through the Sun's corona in early 2021, the spacecraft flew by coronal streamers.
Upon the eruption of a coronal mass ejection (CME), the overlying helmet streamer deforms becoming the CME's leading edge. Similarly, the helmet streamer's cavity becomes the CME's cavity and the helmet streamer's prominence becomes the CME's core.[5]
Pseudostreamersedit
Structures in the corona, similar to a helmet streamer, but connecting holes of the same magnetic polarity, are called pseudostreamers.[6][7][8][9] They were first observed using space-borne coronagraphs and called a "plasma sheets" by Hundhausen (1972). They were later renamed to "unipolar streamers" by Zhao & Webb (2003) and then termed "pseudostreamers" by Wang et al. (2007).[6] Pseudostreamers' structure was observed in 2012 by the Solar Dynamics Observatory.[8]
Magnetic topology of pseudostreamers was described as "contain[ing] twin filaments at its base. Such twin filaments are topologically connected, sharing a neutral point and a separatrix dome. This was a case in which two polarity reversal boundaries contain between them fields with a polarity opposite to that of the global unipolar configuration surrounding them (tripolar pseudostreamer)."[9]
Single hybrid magnetic structure that consists of double-streamer/pseudostreamer was observed in the solar corona on May 5-10, 2013 by the SWAP instrument of the PROBA2 satellite. Its structure was described by researchers:[10]
It consists of a pair of filament channels near the south pole of the Sun. On the western edge of the structure, the magnetic morphology above the filaments is that of a side-by-side double streamer, with open field between the two channels. On the eastern edge, the magnetic morphology is that of a coronal pseudostreamer without the central open field.
^ abKallenrode, May-Britt (2004). Space Physics: An Introduction to Plasmas and Particles in the Heliosphere and Magnetospheres. Berlin: Springer. p. 145. ISBN3-540-20617-5.
^ abWang, Y.-M.; Sheeley, N. R.; Socker, D. G.; Howard, R. A.; Rich, N. B. (1 November 2000). "The dynamical nature of coronal streamers". Journal of Geophysical Research: Space Physics. 105 (A11): 25133–25142. Bibcode:2000JGR...10525133W. doi:10.1029/2000JA000149.
^Cranmer, Steven R. (2009). "Coronal Holes". Living Reviews in Solar Physics. 6 (1): 3. arXiv:0909.2847. Bibcode:2009LRSP....6....3C. doi:10.12942/lrsp-2009-3. PMC4841186. PMID 27194961.
^ abGopalswamy, N. (January 2003). "Coronal mass ejections: Initiation and detection" (PDF). Advances in Space Research. 31 (4): 869–881. Bibcode:2003AdSpR..31..869G. doi:10.1016/S0273-1177(02)00888-8. Retrieved 27 August 2021.
^ abScott, Roger B.; Pontin, David I.; Antiochos, Spiro K.; DeVore, C. Richard; Wyper, Peter F. (1 May 2021). "The Dynamic Formation of Pseudostreamers". The Astrophysical Journal. 913 (1): 64. Bibcode:2021ApJ...913...64S. doi:10.3847/1538-4357/abec4f. S2CID 235281960. Material was copied from this source, which is available under a Creative Commons Attribution 4.0
^Wang, Y.-M.; Sheeley, Jr., N. R.; Rich, N. B. (April 2007). "Coronal Pseudostreamers". The Astrophysical Journal. 658 (2): 1340–1348. Bibcode:2007ApJ...658.1340W. doi:10.1086/511416. S2CID 250768165.
^ abMasson, Sophie; McCauley, Patrick; Golub, Leon; Reeves, Katharine K.; DeLuca, Edward E. (13 May 2014). "Dynamics of the Transition Corona". The Astrophysical Journal. 787 (2): 145. arXiv:1301.0740. Bibcode:2014ApJ...787..145M. doi:10.1088/0004-637X/787/2/145. hdl:2060/20150008396. S2CID 119182452.
^ abPanasenco, Olga; Martin, Sara F.; Velli, Marco; Vourlidas, Angelos (2012). "Origins of Rolling, Twisting, and Non-radial Propagation of Eruptive Solar Events". Solar Physics. 287 (1–2): 391–413. arXiv:1211.1376. doi:10.1007/s11207-012-0194-3. S2CID 118374791.
^Rachmeler, L. A.; Platten, S. J.; Bethge, C.; Seaton, D. B.; Yeates, A. R. (1 May 2014). "Observations of a Hybrid Double-streamer/Pseudostreamer in the Solar Corona". The Astrophysical Journal. 787 (1): L3. arXiv:1312.3153. Bibcode:2014ApJ...787L...3R. doi:10.1088/2041-8205/787/1/L3. hdl:10023/5318. ISSN 0004-637X. Retrieved 10 March 2023.
January 01, 1970
helmet, streamer, also, known, coronal, streamers, elongated, cusp, like, structures, corona, which, often, visible, white, light, coronagraphs, during, solar, eclipses, they, closed, magnetic, loops, which, above, divisions, between, regions, opposite, magnet. Helmet streamers also known as coronal streamers are elongated cusp like structures in the Sun s corona which are often visible in white light coronagraphs and during solar eclipses They are closed magnetic loops which lie above divisions between regions of opposite magnetic polarity on the Sun s surface The solar wind elongates these loops to pointed tips which can extend a solar radius or more into the corona 1 Helmet streamers during a total solar eclipse photographed using exposure bracketing to show both the Sun s corona and the surface features of the new moon itself illuminated by earthshine A few solar prominences are visible around the lunar limb During solar minimum helmet streamers are found closer to the heliographic equator whereas during solar maximum they are found more symmetrically distributed around the Sun Contents 1 Structure 2 Solar cycle 3 Role in coronal mass ejections 4 Pseudostreamers 5 See also 6 ReferencesStructure edit nbsp Helmet streamers appear bright in white light relative to the surrounding coronal plasma Helmet streamers have cusp like bases that taper radially outward away from the Sun forming long stalks The base typically extends up to 1 5 solar radii above the surface whereas the stalk stretched outward by the solar wind can extend over many solar radii 2 Helmet streamers are structured by closed magnetic fields and lie above boundaries separating opposite magnetic polarity in the Sun s photosphere Their thin stalks consist of oppositely directed magnetic fields which form current sheets 3 Surrounding these stalks are open oppositely directed magnetic fields which are anchored to coronal holes lower in the corona 4 The white light emissions of helmet streamers is due to the high electron density of the confined plasma relative to the surrounding corona Light from the photosphere is Thomson scattered off of these electrons with the intensity of scattered light depending on the number of electrons along the observer s line of sight 5 Small blobs of plasma or plasmoids are sometimes released from the tips of helmet streamers and this is one source of the slow component of the solar wind 1 better source needed Solar cycle editFurther information Solar cycle Around solar minimum the point of minimum solar activity during the 11 year solar cycle helmet streamers are generally located around the heliographic equator in what is referred to as the streamer belt At the same time large coronal holes are present at the poles As solar activity increases near the solar maximum helmet streamers appear more symmetrically around the Sun 3 nbsp Solar minimum nbsp Solar maximumCoronagraphs taken near the solar minimum between solar cycles 22 and 23 and near the solar maximum of solar cycle 23 demonstrate the different distributions of helmet streamers around the solar disk at different points in a solar cycle Role in coronal mass ejections edit source source source source source source source As Parker Solar Probe passed through the Sun s corona in early 2021 the spacecraft flew by coronal streamers Further information Coronal mass ejection Upon the eruption of a coronal mass ejection CME the overlying helmet streamer deforms becoming the CME s leading edge Similarly the helmet streamer s cavity becomes the CME s cavity and the helmet streamer s prominence becomes the CME s core 5 Pseudostreamers editStructures in the corona similar to a helmet streamer but connecting holes of the same magnetic polarity are called pseudostreamers 6 7 8 9 They were first observed using space borne coronagraphs and called a plasma sheets by Hundhausen 1972 They were later renamed to unipolar streamers by Zhao amp Webb 2003 and then termed pseudostreamers by Wang et al 2007 6 Pseudostreamers structure was observed in 2012 by the Solar Dynamics Observatory 8 Magnetic topology of pseudostreamers was described as contain ing twin filaments at its base Such twin filaments are topologically connected sharing a neutral point and a separatrix dome This was a case in which two polarity reversal boundaries contain between them fields with a polarity opposite to that of the global unipolar configuration surrounding them tripolar pseudostreamer 9 Single hybrid magnetic structure that consists of double streamer pseudostreamer was observed in the solar corona on May 5 10 2013 by the SWAP instrument of the PROBA2 satellite Its structure was described by researchers 10 It consists of a pair of filament channels near the south pole of the Sun On the western edge of the structure the magnetic morphology above the filaments is that of a side by side double streamer with open field between the two channels On the eastern edge the magnetic morphology is that of a coronal pseudostreamer without the central open field See also editList of solar cycles Coronal loop Solar radio emissionReferences edit a b Kallenrode May Britt 2004 Space Physics An Introduction to Plasmas and Particles in the Heliosphere and Magnetospheres Berlin Springer p 145 ISBN 3 540 20617 5 Koutchmy Serge Livshits Moissei 1992 Coronal streamers Space Science Reviews 61 3 4 393 Bibcode 1992SSRv 61 393K doi 10 1007 BF00222313 S2CID 189775835 Retrieved 30 July 2022 a b Wang Y M Sheeley N R Socker D G Howard R A Rich N B 1 November 2000 The dynamical nature of coronal streamers Journal of Geophysical Research Space Physics 105 A11 25133 25142 Bibcode 2000JGR 10525133W doi 10 1029 2000JA000149 Cranmer Steven R 2009 Coronal Holes Living Reviews in Solar Physics 6 1 3 arXiv 0909 2847 Bibcode 2009LRSP 6 3C doi 10 12942 lrsp 2009 3 PMC 4841186 PMID 27194961 a b Gopalswamy N January 2003 Coronal mass ejections Initiation and detection PDF Advances in Space Research 31 4 869 881 Bibcode 2003AdSpR 31 869G doi 10 1016 S0273 1177 02 00888 8 Retrieved 27 August 2021 a b Scott Roger B Pontin David I Antiochos Spiro K DeVore C Richard Wyper Peter F 1 May 2021 The Dynamic Formation of Pseudostreamers The Astrophysical Journal 913 1 64 Bibcode 2021ApJ 913 64S doi 10 3847 1538 4357 abec4f S2CID 235281960 nbsp Material was copied from this source which is available under a Creative Commons Attribution 4 0 Wang Y M Sheeley Jr N R Rich N B April 2007 Coronal Pseudostreamers The Astrophysical Journal 658 2 1340 1348 Bibcode 2007ApJ 658 1340W doi 10 1086 511416 S2CID 250768165 a b Masson Sophie McCauley Patrick Golub Leon Reeves Katharine K DeLuca Edward E 13 May 2014 Dynamics of the Transition Corona The Astrophysical Journal 787 2 145 arXiv 1301 0740 Bibcode 2014ApJ 787 145M doi 10 1088 0004 637X 787 2 145 hdl 2060 20150008396 S2CID 119182452 a b Panasenco Olga Martin Sara F Velli Marco Vourlidas Angelos 2012 Origins of Rolling Twisting and Non radial Propagation of Eruptive Solar Events Solar Physics 287 1 2 391 413 arXiv 1211 1376 doi 10 1007 s11207 012 0194 3 S2CID 118374791 Rachmeler L A Platten S J Bethge C Seaton D B Yeates A R 1 May 2014 Observations of a Hybrid Double streamer Pseudostreamer in the Solar Corona The Astrophysical Journal 787 1 L3 arXiv 1312 3153 Bibcode 2014ApJ 787L 3R doi 10 1088 2041 8205 787 1 L3 hdl 10023 5318 ISSN 0004 637X Retrieved 10 March 2023 Retrieved from https en wikipedia org w index php title Helmet streamer amp oldid 1219484294, wikipedia, wiki, book, books, library,
