Comments on "Cavitons and spontaneous hot flow anomalies in a hybrid-Vlasov global magnetospheric simulation" by Blanco-Cano et al. (2018)
G\'abor Facsk\'o
TL;DR
This paper critiques a simulation study by Blanco-Cano et al. (2018), arguing that their results do not accurately reproduce the observed transient events in the solar wind, specifically proto-SHFAs, based on simulation limitations.
Contribution
It provides a critical analysis of the previous simulation, clarifying that the simulated features are not the actual transient events observed in the solar wind.
Findings
The simulation failed to reproduce key features of the observed events.
The simulated proto-SHFAs differ from real transient events.
The critique highlights limitations of the VLASIATOR code for this purpose.
Abstract
Blanco-Cano et al. (2018) intended to find a type of transient event in the solar wind before the terrestrial bow shock using a special type of simulation. However, the simulation results cannot reproduce the main features of the event. Based on the remarks described below, I am sure that the features in the simulations are not those type of events. The VLASIATOR code simulated proto-SHFAs.
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\Author
[1]GáborFacskó
1]Rhea System GmbH., TIZ Building, Robert Bosch Str. 7., 64293 Darmstadt, Germany
\correspondence
Gábor Facskó ([email protected])
\pubdiscuss\published
Comment on “Cavitons and spontaneous hot flow anomalies in a hybrid-Vlasov global magnetospheric simulation” by Blanco-Cano et al. (2018)
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The Author
Blanco-Cano et al. (2018) analysed the output of the VLASIATOR global hybrid Vlasov solver and intended to find Spontaneous Hot Flow Anomalies (SHFA, Zhang et al., 2013; Omidi et al., 2013). This is a very nice paper about the development of the foreshock cavitons and magnetosheath cavities based on unique global hybrid-Vlasov simulations. However, the simulation results cannot reproduce the main features of the SHFAs. The SHFAs (and the HFAs) show density and magnetic field magnitude drops in their cavity. The magnetic field is turbulent in the cavity. The temperature is very high in them, a few million K. The solar wind direction turns away from the radial direction and slows down (Facskó et al., 2010; Zhang et al., 2013; Omidi et al., 2013). The latter features gave the name of the phenomenon hence I had serious concerns about whether the Authors had detected SHFA in the paper above.
On Figure 3, 7, 9 of the paper above, the Authors see density and magnetic field drops. The simulated phenomena is not significantly hotter than the surrounding foreshock plasma. The foreshock plasma temperature is never observed at 10 million K. Hence locating in the foreshock cannot be an excuse for the missing feature of the phenomena. The Authors also see “[…] deviations from the bulk solar wind velocity are observed throughout the foreshock, and they are not prominent enough inside SHFAs to be unambiguously identified.” The phenomenon that does not show anomalous flow cannot be called Spontaneous Hot Flow Anomaly.
The SHFAs are surrounded by density and magnetic field increasement at the edge of the phenomena. Their presence proves that the cavity is not in equilibrium and expands. The hybrid simulations of Omidi et al. (2013) could present these shoulders (Lin (2002) could also have simulated them for HFAs). Furthermore, these increasements lead to the observed depletion of the solar wind velocity because the deceleration of the solar wind comes from the bad fitting and plasma moment calculation (Parks et al., 2013; Kecskeméty et al., 2006, Figure 3, 7). Hence, it is possible to explain the missing solar wind deceleration if these increasements are present. If both features are missing, the phenomena cannot be SHFA.
The Authors also study foreshock cavitons, magnetosheath filaments and structures in this paper above. My comments are limited only to the identification and analysis of the “SHFA events” of the simulation. Based on the remarks described above, I am sure that the features in the VLASIATOR simulations are not SHFAs. However, these questionable events could develop to an SHFA. Zhang et al. (2013) observed SHFA–like events without significant solar wind deceleration. As Zhang et al. (2010) discovered and introduced the phenomenon of so called proto-HFA, Zhang et al. (2013) discovered the phenomena of proto-SHFA. These proto-SHFAs were simulated by the VLASIATOR code and misintepreted by the Authors.
Acknowledgements.
Gábor Facskó thanks Sophie Burley for improving the English of the paper.
The reference list from the paper itself. Each links out to its DOI / PubMed record.
- 1Blanco-Cano et al. (2018) Blanco-Cano, X., Battarbee, M., Turc, L., Dimmock, A. P., Kilpua, E. K. J., Hoilijoki, S., Ganse, U., Sibeck, D. G., Cassak, P. A., Fear, R. C., Jarvinen, R., Juusola, L., Pfau-Kempf, Y., Vainio, R., and Palmroth, M.: Cavitons and spontaneous hot flow anomalies in a hybrid-Vlasov global magnetospheric simulation, Annales Geophysicae, 36, 1081–1097, 10.5194/angeo-36-1081-2018 , 2018. · doi ↗
- 2Facskó et al. (2010) Facskó, G., Trotignon, J. G., Dandouras, I., Lucek, E. A., and Daly, P. W.: Study of hot flow anomalies using Cluster multi-spacecraft measurements, Advances in Space Research, 45, 541–552, 10.1016/j.asr.2009.08.011 , 2010. · doi ↗
- 3Kecskeméty et al. (2006) Kecskeméty, K., Erdős, G., Facskó, G., Tátrallyay, M., Dandouras, I., Daly, P., and Kudela, K.: Distributions of suprathermal ions near hot flow anomalies observed by RAPID aboard Cluster, Advances in Space Research, 38, 1587–1594, 10.1016/j.asr.2005.09.027 , 2006. · doi ↗
- 4Lin (2002) Lin, Y.: Global hybrid simulation of hot flow anomalies near the bow shock and in the magnetosheath, Planetary and Space Science, 50, 577–591, 10.1016/S 0032-0633(02)00037-5 , 2002. · doi ↗
- 5Lucek et al. (2004) Lucek, E. A., Horbury, T. S., Balogh, A., Dandouras, I., and RèMe, H.: Cluster observations of hot flow anomalies, Journal of Geophysical Research (Space Physics), 109, A 06207, 10.1029/2003 JA 010016 , 2004. · doi ↗
- 6Omidi et al. (2013) Omidi, N., Zhang, H., Sibeck, D., and Turner, D.: Spontaneous hot flow anomalies at quasi-parallel shocks: 2. Hybrid simulations, Journal of Geophysical Research (Space Physics), 118, 173–180, 10.1029/2012 JA 018099 , 2013. · doi ↗
- 7Parks et al. (2013) Parks, G. K., Lee, E., Lin, N., Fu, S. Y., Mc Carthy, M., Cao, J. B., Hong, J., Liu, Y., Shi, J. K., Goldstein, M. L., Canu, P., Dandouras, I., and Rème, H.: Reinterpretation of Slowdown of Solar Wind Mean Velocity in Nonlinear Structures Observed Upstream of Earth’s Bow Shock, Astrophysical Journal Letters, 771, L 39, 10.1088/2041-8205/771/2/L 39 , 2013. · doi ↗
- 8Sibeck et al. (2002) Sibeck, D. G., Phan, T.-D., Lin, R., Lepping, R. P., and Szabo, A.: Wind observations of foreshock cavities: A case study, Journal of Geophysical Research (Space Physics), 107, 1271, 10.1029/2001 JA 007539 , 2002. · doi ↗