Space Physics and Aeronomy, Ionosphere Dynamics and Applications. Группа авторов
“hot” patches with higher electron temperature have also been observed and further studies are needed to distinguish the classical cold and hot patches, in particular, whether they are generated due to different mechanisms or produced by similar mechanisms but evolve under different precipitating particle and field‐aligned current environments. In the future, it may be more sensible to treat the relatively lower‐density patches and higher‐density patches separately, since they might be produced by different mechanisms, and the similarities and differences of their evolution, as well as their relationship with the hot and cold patches, are of great interest.
In the polar cap region, the dynamic evolution of the high‐density structures is mainly controlled by the convection pattern and their fate after they enter the polar cap would be determined by a sequence of convection patterns controlled mainly by the IMF. The patches exit the polar cap nearly symmetrically around midnight, but indeed show clear preference for dusk or dawn sectors under positive or negative IMF By. Besides the horizontal transport, significantly enhanced type‐1 and type‐2 ion upflow fluxes associated with these high‐density structures have also been observed. The impact of large but intermittent ion upflow/outflow fluxes associated with polar cap patches and TOI on magnetospheric dynamics is of great interest and would require close collaboration between the aeronomy and magnetospheric physics communities.
Enhanced 630 nm airglow emissions due to recombination are often used to image the polar cap high‐density structures. However, besides the recombination‐induced 630 nm emission, other mechanisms can also lead to variations in 630 nm emission, such as soft electron precipitation, thermal excitation, and lifting or descending of the F‐region height. Therefore, care is needed when interpreting the 630 nm emission variations, and it is better to be combined with other diagnosis tools, such as electron temperature. The relative contributions of those mechanisms to the total patch emission under various conditions and for different types of patch should be further explored.
ACKNOWLEDGMENTS
S. Zou would like to acknowledge NASA grant NNX14AF31G, NSF grant AGS 1400998 and NASA grant 80NSSC20K1313. G. W. Perry acknowledges the support from the Natural Science and Engineering Research Council of Canada (NSERC) Discovery Grant RGPIN/06069‐2014.
REFERENCES
1 Aa, E., Liu, S., Huang, W., Shi, L., Gong, J., Chen, Y., et al. (2016). Regional 3‐D ionospheric electron density specification on the basis of data assimilation of ground‐based GNSS and radio occultation data: Regional 3‐D ionosphere specification. Space Weather, 14(6), 433–448. doi:10.1002/2016SW001363
2 Aa, E., Ridley, A., Huang, W., Zou, S., Liu, S., Coster, A. J., & Zhang, S. (2018). An ionosphere specification technique based on data ingestion algorithm and empirical orthogonal function analysis method: Madrigal TEC ingestion into NeQuick and EOF analysis. Space Weather. doi:10.1029/2018SW001987
3 Anderson, D. N., Buchau, J., & Heelis, R. A. (1988). Origin of density enhancements in the winter polar cap ionosphere. Radio Science, 23(4), 513–519. doi:10.1029/RS023i004p00513
4 Bust, G. S., & Datta‐Barua, S. (2014). Scientific investigations using IDA4D and EMPIRE. In J. Huba, R. Schunk, & G. Khazanov (Eds.), Modeling the ionosphere‐thermosphere system (pp. 283–297). Geophysical Monograph Series. Chichester, UK: John Wiley & Sons, Ltd. doi:10.1002/9781118704417.ch23
5 Bust, G. S., & Mitchell, C. N. (2008). History, current state, and future directions of ionospheric imaging. Reviews of Geophysics, 46(1). doi:10.1029/2006RG000212
6 Carlson, H. C. (1994). The dark polar ionosphere: Progress and future challenges. Radio Science, 29(1), 157–165. doi:10.1029/93RS02125
7 Carlson, H. C. (2004). Ionospheric patch formation: Direct measurements of the origin of a polar cap patch. Geophysical Research Letters, 31(8). doi:10.1029/2003GL018166
8 Carlson, H. C. (2012). Sharpening our thinking about polar cap ionospheric patch morphology, research, and mitigation techniques: Patch research and mitigation techniques. Radio Science, 47(4). doi:10.1029/2011RS004946
9 Carlson, H. C., Moen, J., Oksavik, K., Nielsen, C. P., McCrea, I. W., Pedersen, T. R., & Gallop, P. (2006). Direct observations of injection events of subauroral plasma into the polar cap. Geophysical Research Letters, 33(5). doi:10.1029/2005GL025230
10 Chartier, A. T., Mitchell, C. N., & Miller, E. S. (2018). Annual occurrence rates of ionospheric polar cap patches observed using swarm: Annual occurrence rates of ionospheric polar cap patches observed using Swarm. Journal of Geophysical Research: Space Physics. doi:10.1002/2017JA024811
11 Coley, W. R., & Heelis, R. A. (1998). Structure and occurrence of polar ionization patches. Journal of Geophysical Research: Space Physics, 103(A2), 2201–2208. doi:10.1029/97JA03345
12 Coster, A. J., Gaposchkin, E. M., & Thornton, L. E. (1992). Real‐Time Ionospheric Monitoring System Using GPS. Navigation, 39(2), 191–204. doi:10.1002/j.2161‐4296.1992.tb01874.x
13 Crowley, G. (1996). A critical review of ionospheric patches and blobs. In Review of radio science 1993–1999 (pp. 619–648). New York: Oxford University Press.
14 Dahlgren, H., Perry, G. W., Semeter, J. L., St. Maurice, J. P., Hosokawa, K., Nicolls, M. J., et al. (2012a). Space‐time variability of polar cap patches: Direct evidence for internal plasma structuring: Variability of polar cap patches. Journal of Geophysical Research: Space Physics, 117(A9). doi:10.1029/2012JA017961
15 Dahlgren, H., Semeter, J. L., Hosokawa, K., Nicolls, M. J., Butler, T. W., Johnsen, M. G., et al. (2012b). Direct three‐dimensional imaging of polar ionospheric structures with the Resolute Bay Incoherent Scatter Radar: The 3D imaging of polar ionospheric structures. Geophysical Research Letters, 39(5). doi:10.1029/2012GL050895
16 David, M., Sojka, J. J., Schunk, R. W., & Coster, A. J. (2016). Polar cap patches and the tongue of ionization: A survey of GPS TEC maps from 2009 to 2015: Patches and the TOI: GPS TEC maps. Geophysical Research Letters, 43(6), 2422–2428. doi:10.1002/2016GL068136
17 Fairfield, D. H., & Scudder, J. D. (1985). Polar rain: Solar coronal electrons in the Earth's magnetosphere. Journal of Geophysical Research, 90(A5), 4055. doi:10.1029/JA090iA05p04055
18 Foster, J. C. (1984). Ionospheric signatures of magnetospheric convection. Journal of Geophysical Research, 89(A2), 855. doi:10.1029/JA089iA02p00855
19 Foster, J. C. (1993). Storm time plasma transport at middle and high latitudes. Journal of Geophysical Research: Space Physics, 98(A2), 1675–1689. doi:10.1029/92JA02032
20 Foster, J. C., & Doupnik, J. R. (1984). Plasma convection in the vicinity of the dayside cleft. Journal of Geophysical Research, 89(A10), 9107. doi:10.1029/JA089iA10p09107
21 Foster, J. C., Coster, A. J., Erickson, P. J., Holt, J. M., Lind, F. D., Rideout, W., et al. (2005). Multiradar observations of the polar tongue of ionization: Multiradar observations. Journal of Geophysical Research: Space Physics, 110(A9). doi:10.1029/2004JA010928
22 Foster, J. C., Erickson, P. J., Baker, D. N., Claudepierre, S. G., Kletzing, C. A., Kurth, W., et al. (2014). Prompt energization of relativistic and highly relativistic electrons during a substorm interval: Van Allen Probes observations: Rapid relativistic electron energization. Geophysical Research Letters, 41(1), 20–25. doi:10.1002/2013GL058438
23 Foster, J. C., Holt, J. M., Kelly, J. D., & Wickwar, V. B. (1985). High‐Resolution observations of electric fields and F‐region plasma parameters in the cleft ionosphere. In J. Holtet and A. Egeland (Eds.), The polar cusp (pp. 349–364). Springer. doi: 10.1007/978‐94‐009‐5295‐9
24 Gardner, L. C., Schunk, R. W., Scherliess, L., Eccles, V., Basu, S., & Valladeres, C. (2018). Modeling the mid‐latitude ionosphere storm enhanced density distribution with a data assimilation model. Space Weather. doi:10.1029/2018SW001882
25 Gardner, L. C., Schunk, R. W., Scherliess, L., Sojka, J. J., & Zhu, L. (2014). Global assimilation of ionospheric measurements, Gauss Markov model: Improved specifications with multiple