GEOMAGNETIC STORM WATCH (G1-CLASS)

Jan 27, 2020
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A Coronal Mass Ejection (CME) is heading for Earth. Minor G1-class storms are possible when the storm cloud arrives on March 28th. Coronagraphs onboard the Solar and Heliospheric Observatory (SOHO) made this movie as the CME left the sun on March 25th:

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The CME is faint, but it is moving fast (959 km/s) squarely inside the Earth strike zone. It could deliver a sharp blow to our planet's magnetic field despite its low luminosity in the coronagraph movie.

NASA analysts have modeled the CME's trajectory. Note the yellow dot in the animation below. That's Earth.

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If NASA's model is correct, the CME will miss Venus on March 27th before hitting Earth around 0 hours UT on March 28th. For observers in North America, this means the geomagnetic storm could begin after local nightfall on Sunday, March 27th. Photographic auroras could descend into northern-tier US states from Maine to Washington. Aurora alerts: SMS Text.

This is a good time of year for aurora watchers. During the weeks around equinoxes, cracks form in Earth's magnetic field, allowing solar wind to enter. Even a weak CME impact can spark a good display at high latitudes. Researchers call it the "Russell-McPherron effect*," and it could boost the effectiveness of the incoming CME. Stay tuned!

See: https://spaceweather.com

*Russell-McPherron effect: The best physical manifestation of the Russell – McPherron effect is the Auroras. The scientific community named the phenomenon after Professor Christopher T. Russell and Professor Emeritus Robert L. McPherron from the University of California, Los Angeles (UCLA). Aurora’s appear because of the particle bombardment of the magnetosphere. Whenever the accelerating solar wind comes in contact with the earth’s magnetic field and enters the poles, the particles interact with the atmosphere gases, thus we see the discharges as curtains of lights. Now, the Russell – McPherron phenomenon suggests an increase in geomagnetic activity or disturbance during the equinoxes because the Earth’s magnetic field in the poles momentarily cracks open.

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Bar Graph on Geomagnetic Disturbance from 1932 to 2007

While it is well known that high fluxes of relativistic electrons in the Earth's radiation belts are associated with high-speed solar wind and its heightened geoeffectiveness, less known is the fact that the Russell McPherron(R M) effect strongly controls whether or not a given high-speed stream is geoffective.

To test whether it then follows that the R M effect also strongly controls fluxes of relativistic electrons, we perform a superposed epoch analysis across co-rotating interaction regions (CIR) keyed on the interfaces between slow and fast wind. A total of 394 stream interfaces were identified in the years 1994-2006. Equinoctial interfaces were separated into four classes based on the R-M effect,that is, whether the solar wind on either side of the interface was either(geo)effective (E) or ineffective (I) depending on season and the polarity of the interplanetary magnetic field (IMF). Four classes of interface identified as II, IE, EI,and EE are possible. The classes IE and EI correspond to CIRs with polarity changes indicating passage through the heliospheric current sheet. To characterize the behavior of solar wind and magnetospheric variables, we produced maps of dynamic cumulative probability distribution functions (cdfs) as a function of time over 10-day intervals centered on the interfaces. These reveal that effective high-speed streams have geomagnetic activity nearly twice as strong as ineffective streams and electron fluxes a factor of 12 higher. In addition they show that an effective low-speed stream increases the flux of relativistic electrons before the interface so that an effective to ineffective transition results in lower fluxes after the interface. We conclude that the R-M effect plays a major role in organizing and sustaining a sequence of physical processes responsible for the acceleration of relativistic electrons along the lines of magnetic flux in the Earth's magnetic field.

See: https://theastrojunkie.wordpress.com/2021/03/02/the-russell-mcpherron-phenomenon-the-likely-science-behind-the-ingresses-of-mundane-astrology/comment-page-1/

See: https://ntrs.nasa.gov/citations/20100015565

The following from: R.L. McPherron et al. / Journal of Atmospheric and Solar-Terrestrial Physics 71 (2009) 1032–1044

Early in the space era one of the first polar orbiting spacecraft 1963 38C revealed the presence of a 27-day periodicity in the flux of relativistic electrons (E41.2MeV) at radial distances larger than 3 Re. Williams (1966) correlated temporal profiles of electron intensity from this spacecraft with the newly discovered inter- planetary magnetic field (IMF) sector structure (Ness and Wilcox, 1965). He demonstrated that peaks in intensity occurred at or a little after the sector crossings, but only at boundaries where the IMF switched from negative (toward Sun) to positive (away from Sun). Wilcox and Ness (1965) had demonstrated that many solar wind parameters including velocity, field strength, density, as well as geomagnetic activity were organized by sector boundaries.
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While it is well known that high fluxes of relativistic electrons in the Earth’s radiation belts are associated with high-speed solar wind and its heightened geoeffectiveness, less known is the fact that the Russell–McPherron (R–M) effect strongly controls whether or not a given high-speed stream is geoffective. To test whether it then follows that the R–M effect also strongly controls fluxes of relativistic electrons, we perform a superposed epoch analysis across corotating interaction regions (CIR) keyed on the interfaces between slow and fast wind. A total of 394 stream interfaces were identified in the years 1994–2006. Equinoctial interfaces were separated into four classes based on the R–M effect, that is, whether the solar wind on either side of the interface was either (geo)effective (E) or ineffective (I) depending on season and the polarity of the interplanetary magnetic field (IMF). Four classes of interface identified as II, IE, EI, and EE are possible. The classes IE and EI correspond to CIRs with polarity changes indicating passage through the heliospheric current sheet. To characterize the behavior of solar wind and magnetospheric variables, we produced maps of dynamic cumulative probability distribution functions (cdfs) as a function of time over 10-day intervals centered on the interfaces. These reveal that effective high-speed streams have geomagnetic activity nearly twice as strong as ineffective streams and electron fluxes a factor of 12 higher. In addition they show that an effective low-speed stream increases the flux of relativistic electrons before the interface so that an effective to ineffective transition results in lower fluxes after the interface. We conclude that the R–M effect plays a major role in organizing and sustaining a sequence of physical processes responsible for the acceleration of relativistic electrons.
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Based on these results Williams explained the intensity peak after the 􏰁 to + transitions as a consequence of a peak in the Alfve ́ n Mach number of the solar wind that occurred at only these times.

Eleven years later Paulikas and Blake (1979) studied the behavior of relativistic electrons at synchronous orbit near solar minimum and found that flux increases were highly correlated with solar wind speed and the IMF sector structure. Specifically they found that the electron fluxes begin to increase about a day after arrival of the high-speed stream and reach their maximum about 2–3 days later. They also noted: ‘‘A well-ordered stream pattern gives rise to a regular sequence of electron flux growth and decay y’’ Furthermore, they observed larger increases in fall for away sectors and in spring for toward sectors. They speculated that the Russell–McPherron (R–M) effect (Russell and McPherron, 1973) could explain this dependence on IMF sector structure. Baker et al. (1986) called attention to the fact that the high-speed solar wind is associated with corotating interactions regions (CIR) during the declining phase of the solar cycle and speculated that a pair of CIRs might form a ‘‘wave guide’’ allowing Jovian electrons to reach Earth. Subsequently, Baker et al. (1989) presented evidence that the acceleration of electrons to relativistic energies is an internal magnetospheric process.

Nagai (1988) demonstrated the truth of the previous suggestion with synchronous observations of relativistic electron fluxes and magnetic indices. Using superposed epoch analysis he showed that electron fluxes reach a minimum at the time of minimum Dst and maximum Kp. He then demonstrated that a linear prediction filter with Kp as input can predict more that half the variance of the daily average flux. These results suggested the possibility that stronger activity, i.e. magnetic storms, would produce larger fluxes of relativistic electrons. Note, however, that Baker et al. (1990) showed that the solar wind speed is an equally good predictor of electron fluxes, and that AE does not do as well as speed or Kp. Later Reeves (1998) explicitly considered the possibility that magnetic storms are responsible for the accelera- tion of relativistic electrons. He concluded that more than a storm is needed.

‘‘... but that there is some additional factor, either in the solar wind or in the magnetosphere, that determines whether a given storm will produce relativistic electrons or not and how strong that response will be.’’

O’Brien et al. (2001a) examined a very large set of magnetic storms and found that the best predictors of high fluxes are solar wind speed 4450 km/s, Pc 5 wave power 41000 nT2 and long duration of the storm recovery phase. The strength of the ring current was not a good predictor. Reeves et al. (2003) examined this question further finding that only half of all storms accelerate electrons and that the ratio of pre- to post-storm fluxes is nearly independent of the strength of storms. They conclude:

‘‘However, for all solar wind velocities both increases and decreases were still observed. Our analysis suggests that the effect of geomagnetic storms on radiation belt fluxes are a delicate and complicated balance between the effects of particle acceleration and loss.’’

In this paper we will demonstrate that previously neglected factors include season and polarity of the interplanetary magnetic field.

With the advent of long duration spacecraft missions it became possible to perform more detailed analysis of the temporal properties of relativistic electrons. Baker et al. (1999b) demonstrated that electron fluxes measured by both the low-altitude SAMPEX satellite, and the high-altitude Polar spacecraft exhibit very pronounced semiannual variations of electron fluxes. Using quarterly averages centered on the equinoxes and solstices they found that fluxes were nearly 3 times higher at the equinoxes than at the solstices. They attributed this to the Russell–McPherron effect but noted the modulation of electron fluxes was much stronger than it is for geomagnetic activity. In discussing their result they called attention to the fact that the correlation of electron fluxes with solar wind velocity might indicate that low- frequency ULF waves are produced by the Kelvin–Hemholtz (K–H) instability during high-speed streams (Rostoker et al., 1998). They therefore suggested the following model to explain the observations.

During the declining phase of the solar cycle large coronal holes produce high-speed solar wind streams. When these streams hit Earth they cause substorms when the IMF is south- ward in gsm coordinates as a consequence of the Russell– McPherron effect and other factors. The substorms inject seed populations of low-energy electrons into the inner magneto- sphere. ULF waves in the Pc 5 band produced by the K–H instability radially diffuse the electrons inward increasing the electron energy to relativistic values.
Current ideas about electron acceleration are more sophisti- cated (Horne et al., 2006) but do not deal directly with the topic of this paper—the role of the Russell–McPherron effect. In the following we use data from two solar cycles to demonstrate that the basic idea proposed by Baker et al. is correct, but there are additional factors associated with corotating interaction regions that need to be considered. We begin with a review of the Russell–McPherron effect.

In the early 1970s the concept of magnetic reconnection as the cause of geomagnetic activity was not universally accepted. Consequently it was important to examine implications of the hypothesis and determine if they were supported by data. To this end Russell and McPherron (1973) noted that the semiannual variation of geomagnetic activity with peaks at the equinoxes might be explained by magnetic reconnection. Their argument was geometrical and is illustrated in Fig. 1. At the top left of the figure the circle represents the orbit of the Earth around the Sun in the ecliptic plane. The Earth is shown at spring equinox on 21 March. At this time the rotation axis of the Earth is pointed 23.441 away from its orbital velocity vector and is orthogonal to the Earth–Sun line. A few weeks earlier (5 March) the rotation axis of the Sun is tilted directly away from Earth so that Earth is located at 7.251 south heliographic latitude. The interplanetary magnetic field generally lies in the solar equatorial plane and is wrapped into a spiral as a consequence of the radial flow of the solar wind and the rotation of the Sun. The geocentric solar ecliptic (gse) coordinate system is shown in the lower left of the figure. This coordinate system is centered in the Earth with the X-axis always pointing directly to the center of the Sun. The Z-axis points to the north ecliptic pole and the Y-axis is orthogonal to both, and antiparallel to Earth’s orbital velocity. A spiral magnetic field toward the Sun as shown in the top panel is depicted by the vector labeled ‘‘Toward’’. Note that this vector has a negative projection on the gse Y-axis. The bottom right panel shows the geometry as viewed along the gse X-axis toward the Sun. The

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Fig. 1. An illustration of the geometry of the spiral magnetic field of the solar wind and how it is converted to a geomagnetically effective southward component at Earth at spring and fall equinox.

Earth’s rotation axis is tilted 23.441 away from Z toward the Y-axis. At 2247 UT on 19 March the dipole axis lies in the Y–Z plane at an angle of 34.81 to the Z-axis. The projection of the Y-component of the spiral magnetic field onto the direction of the dipole is negative and magnetic reconnection between the IMF and the dipole magnetic field is expected. Reconnection drives internal flows in the magnetosphere and produces magnetospheric sub- storms responsible for geomagnetic activity.

It has been found that phenomena within the magnetosphere are generally controlled by the orientations of the Sun vector and the dipole axis. The geocentric solar magnetospheric (gsm) coordinate system is defined in terms of these two vectors. X points to the Sun as in gse coordinates. The Z-axis is orthogonal to X but is rotated about X so that the dipole always lies in the X–Z plane. At the time assumed in the drawing the dipole and gsm Z-axis are coincident. At other times the dipole will lie in front or behind the gsm Y–Z plane. As Earth rotates and progresses around the Sun the relative orientation of these coordinates systems change. For example, at summer solstice (second ball in top panel) Earth’s rotation axis lies in the gse X–Z plane and an ecliptic IMF will have no projection onto the gsm Z-axis. Thus no magnetic activity is expected as a result of geometric projection effects.

At fall equinox the gse coordinate system has rotated 1801 about the ecliptic pole. At this time only ‘‘Away’’ sectors of the IMF will project onto the gsm Z-axis with a negative projection. Also, the universal time of maximum dipole tilt away from the gse Z-axis is 􏰂12 h later (1032 UT on 22 September). These facts lead to the Russell–McPherron rule ‘‘Spring To Fall Away’’ as the orientation of the IMF that produce geomagnetic activity at Earth.
This entire argument is made more complicated by the tilt of the Sun’s rotation axis because the spiral IMF actually lies in the solar equatorial plane. Another coordinate system is needed to describe this fact (geocentric solar equatorial or gseq). This difference changes the day and universal time at which the maximum projection of the spiral IMF occurs at Earth. The spring peak actually occurs at 22:35 on 7 April and the fall peak at 10:20 on 11 October. A second complication arises from the fact that in general slow-speed solar wind originates near the solar magnetic equator while high-speed solar wind comes from higher and lower heliographic latitudes (Phillips et al., 1995). It is possible that activity at the equinox is enhanced by a high solar wind velocity rather than the R–M effect. This suggestion is know as the ‘‘axial effect’’ (Cliver et al., 2000). A third complication is the argument by Cliver et al. (2000) that the coupling efficiency between the solar wind and Earth is reduced at solstices relative to that at equinox because the angle in the X–Z plane between the solar wind velocity and the Earth’ dipole is not 901. Paradoxically this is named the ‘‘equinoctial hypothesis’’.

See: http://www.igpp.ucla.edu/public/rmcpherr/McPherronPDFfiles/McPherron_RoleRusMcPEffect_2009.pdf

There is an old New England saying: Dawn breaks over Marblehead. In this case, as dawn breaks for me, I finally realize that Professors Russel and McPherron have provided the physics behind why March and April and September and November see the spike in the auroral activity. The McPherron, et al, article from 2009, above, further flashes this idea out.
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