The Solar wind originates from the Coronal Holes (CHs) associated with open field lines, the fast coronal wind is associated with them in the polar regions with speeds varying between 700 - 800 km/s and slow solar wind is associated with the CHs located in the equatorial regions with speeds ~400 km/s. The solar wind expands continuously in interplanetary space and its interaction with the planetary magnetic field creates the planetary magnetospheres. In general, the magnetosphere size is determined by the balance between solar wind dynamic pressure and the magnetic field planetary pressure (Rodríguez-Gómez, 2021 [1] and references therein).

Jupiter has a magnetic field ten times higher than the Earth’s magnetic field, as result its magnetosphere reaches 150 R_J (R_J = 71,492 km) and its radiation belts are the strongest in the solar system (Plainaki et al. 2016 [2] , Bunce et al. 2004 [3] ).

The solar wind interaction with Jupiter’s magnetosphere is still under debate (e.g., Cowley et al. 2008 [4] ; McComas & Bagenal, 2007 [5] ). But observations and theory suggest that is quite different from the Earth’s magnetosphere because of the large spatial scales, rapid planetary rotation, and plasma sources in the magnetosphere (Vogt et al. 2019 [6] ). The first studies of the Jovian magnetosphere started in the seventies, e.g., Brice and Ioannidis, 1970 [7] , who applied ideas from the terrestrial magnetosphere to Jupiter. They point out that the strong magnetic field of Jupiter dominates the magnetopause, making a rotation-dominated Jovian magnetosphere. By the early 1980s was clear that the Jovian magnetosphere is dominated by an internal source—the Io torus rather than the planet’s atmosphere (Delamere and Bagenal, 2010 [8] ).

The relationship between auroral radio emissions and solar wind interaction with Jupiter’s magnetosphere is not trivial. Observations consistently show that solar wind interactions and aurorae brightness are positively correlated at Jupiter (Badman et al. 2016 [9] ; Dunn et al. 2016 [10] ; Panchenko et al. 2013 [11] ; Hess et al. 2012 [12] ; Echer et al. 2010 [13] ; Nichols et al. 2009 [14] ). Additionally, Chané et al. 2017 [15] show their simulations agree with observations, which consistently show that solar wind perturbations and aurora brightness are positively correlated.

The solar wind power on the magnetospheric cross section is the primary energy source of auroral radio emissions, except for those of the Io-Jupiter system (Zarka, P. 1998 [16] ). In general, Jovian Auroral Radio Emissions (AREs) have three main components: first the broadband kilometer component (bKOM) between ~10 and > 300 kHz, second the hectometer component (HOM) from 300 kHz to a few MHz (peaking about 800 kHz) and third the decameter components, up to 40 MHz. A component is related to the satellite Io (Io-DAM) and another component is independent of Io. It is called non-Io-DAM characterized by the high-frequency extent of HOM emission.

Magnetospheric observations are now available from some spacecraft missions one of the most important is the Galileo orbiter from 1996 to 2003, but in most cases near Jupiter upstream solar wind measurements are unavailable (Vogt et al. 2019 [6] ). This paper aims to study the solar wind’s influence on Jupiter’s magnetosphere using mSWiM solar wind data propagated to Jupiter. For this purpose, we calculate the Interplanetary fast shocks: Forward shocks (FS), Reverse shocks (RS), and solar wind dynamic pressure.

Solar wind data propagated to Jupiter’s orbit will be obtained from the one-dimensional numerical magneto hydrodynamic (MHD) code developed by the University of Michigan (Zieger and Hansen 2008 [17] ). mSWiM is a 1.5-D ideal MHD model implemented with the Versatile Advection Code (VAC), a general software package designed to solve MHD equations in conservative form (Tóth, G. 1996 [18] ). The model propagates the solar wind plasma radially outward from the Earth’s orbit at a selected longitude in the inertial frame of reference, assuming spherical symmetry.

The simulation uses solar wind conditions measured at Earth as the inner boundary. For the solar wind predictions, it uses hourly solar wind plasma and interplanetary magnetic field (IMF) data in the RTN coordinate system from the OMNIWeb database¹ as input. This solution is then mapped to the body of interest, in this case Jupiter, to provide the predicted solar wind conditions. mSWiM has been extensively validated statistically using 12 years of Pioneer, Voyager, Ulysses, and Cassini data from 3.5 to 10 AU. Also, it was able to capture the propagation of transient events like interplanetary coronal mass ejections (ICMEs) even at solar maximum, when the corona is far from the steady state (Zieger and Hansen, 2008 [17] ).

Jupiter’s magnetosphere, in part is sensitive to the solar wind dynamic pressure variations. Several observations showed that aurora and radio emissions are intensified during higher solar wind pressure or induced by interplanetary shocks (Hess et al. 2012 [12] ). ICMEs or CIRS drive interplanetary shocks. The fast forward (FS) shock is caused by ICMEs that originated from CMEs. However, when CHs are evolving, fast streams emanate, and intercept the ambient solar wind. This interaction forms a compression region between the high-speed stream and slow-speed stream; it is limited by fast forward (FS) and fast reverse (RS) shocks (Hess, S. et al. 2014 [19] ).

The interplanetary fast shocks were identified on mSWim data using the characteristics described by Echer et al. 2010 [13] and Echer 2019 [20] . Those shocks are described as follows:

• Fast forward shock (FS) occurs when the solar wind speed v m ( km / s ) , density N ( cm − 3 ) , temperature T ( K ) and magnetic field magnitude B m ( n T ) increase in time.

• Fast reverse shock (RS) is characterized by an increase on solar wind speed with time, while other parameters such as temperature, density, and magnetic field magnitude decrease.

The magnetic field components were obtained from mSWim model. Specifically, the magnetic field magnitude B m ( n T ) was obtained as

B m = B r 2 + B t 2 + B n 2 (1)

The velocity magnitude v m ( km / s ) of solar wind were obtained from the mSWim model.

v m = v r 2 + v t 2 + v n 2 (2)

where subscripts r, t, n, indicate magnetic field and velocity components.

Γ B , Γ N , and v m were calculated, where Γ B = B 2 B 1 and, Γ N = N 2 N 1 , B 2 and N 2 are the magnetic field and density after shock. B 1 and N 1 are the magnetic field and density before the shock (see Appendix 2).

This work selected the apparent opposition periods from 1997 to 2016. This period is defined as the time of opposition of Earth and a given planet, in this case, Jupiter or any other body plus the solar wind propagation time from Earth to the body at an average speed of 500 km/s. The most reliable predictions are expected within 75 days of apparent opposition (Figure 1).

The Interplanetary fast shocks: Forward shocks (FS), and Reverse shocks (RS) were obtained in opposition periods with Jupyter. A period ± 50 days was selected before and after apparent opposition day (Table 1).

± 50 days from the apparent opposition were used in this analysis. The fast shocks from 1997 to 2016 were obtained and analyzed. Figure 2 and Figure 3 show some examples of the detection of interplanetary shocks during the opposition periods. This procedure was applied in all periods described in Table 1. Their respective figures and details are summarized in Appendix 1 and Appendix 2. An analysis of the dynamic pressure in each apparent opposition period was performed (Section 4.1), as well as the mean dynamic pressure variations in time from 1997 to 2016.

The solar wind dynamic pressure was calculated as P s w = m p v s w 2 , where m p is the proton mass, N is the density and v s w is the solar wind speed. The pressure variation is dominated by the density and solar wind speed variation. Each FS and RS shocks, P s w ( n P a ) were calculated at an initial and final point, and their variation was obtained as Δ P s w = P s w f − P s w i .

Figures 4-7 show the dynamic pressure distribution in FS and RS during the opposition periods from 1997 to 2016. The dotted red line denotes the mean value in each distribution. Figure 8 summarizes the mean dynamic pressure ( P s w ) value in time. Dotted vertical lines mark the maximum of solar cycle 23 and 24 and the minimum between both solar cycles. Those intervals were defined previously by Rodríguez-Gómez et al. 2020 [21] , e.g., maximum of solar cycles 23 from 1999 to 2003, maximum of solar cycle 24 from 2011 to 2015, and solar minimum from 2006 to 2010.

The role of the solar wind in Jupiter’s magnetosphere is an open question, specifically how it influences the topology and dynamics (Ebert et al. 2014 [22] and references therein). The main results of this study focused on the solar wind interaction in Jupiter’s magnetosphere can be summarized as follows.

• Five hundred fifteen shocks were obtained from 1997 to 2016 during opposition periods. 58.5% corresponds to fast forward (FS) shocks, and 41.5% are fast reverse (RS) shocks (Table 2).

• The fast forward (FS) shocks were predominant from 1997 to 2016. As well as the dynamic pressure in fast forward shock (FS) during solar cycles 23 and 24. It can imply that the magnetospheric disturbance caused by FS shocks is considerably higher than RS shocks. It is related to the intrinsic characteristics of FS shocks because all physical quantities such as velocity, magnetic field, density, and temperature increase in time increasing the dynamic pressure.

• The relationship between the solar cycle, fast forward, and reverse shocks is summarized in Figure 7. In general, both kinds of shocks follow the solar cycle. FS shocks show a high value on the maximum of solar cycle 23 compared to the maximum of solar cycle 24. However, RS shocks show a similar behavior during the maximum solar cycles 23 and 24.

• An important aspect is correlating the solar wind features and the in-situ measurements in Jupiter’s magnetosphere. It was explored before by Vogt et al. 2019 [6] using Galileo data during orbit E16 and C9 and mSWim data. These periods show a good agreement between the magnetospheric compression and the high solar wind dynamic pressure. The idea is to extend this analysis using in-situ data from other missions and describe the impact of solar wind in the planetary’s magnetosphere.

• Jupiter is a complex system; e.g., internal sources such as Io mainly control the auroral radio and UV emissions, but the solar wind influence can be considered in that kind of emissions to understand their effect. As well as the correlation between solar wind pressure at Jupiter’s magnetosphere and the intensity of the auroral radio emission (e.g., using the Nancay array) can help to understand the relationship between the solar wind and Jupiter’s auroral dynamics. Additionally, a study about the Solar Energetic Particles (SEPs) reaching Jupiter’s magnetosphere is very valuable to evaluate their influence.

J. M. R. G. thanks Ezequiel Echer for the fruitful discussions. This work was supported by NASA Goddard Space Flight Center through Cooperative Agreement 80NSSC21M0180 to Catholic University, Partnership for Heliophysics and Space Environment Research (PHaSER).

The author declares no conflicts of interest regarding the publication of this paper.

Rodríguez-Gómez, J.M. (2023) Solar Wind Interaction with Jupiter’s Magnetosphere. Advances in Aerospace Science and Technology, 8, 34-54. https://doi.org/10.4236/aast.2023.83004

Interplanetary fast shocks covering the period described above.

Detailed information about FS and RS shocks from 1997 to 2016. Initial and final shock time (hrs), DOY, shock type, the Γ B = B 2 / B 1 , Γ N = N 2 / N 1 , where B 2 and N 2 are the magnetic field and density after shock, B 1 and N 1 is the magnetic field and density before shock. Details see: https://we.tl/t-x3iN9LFfUc.