I understand that the solar wind follows the Parker spiral shape of the Sun's magnetic field, thus it is possible for solar wind from a point on the opposite side of the Sun to reach Earth.

I have seen it argued that solar energetic particles (SEPs) from a solar flare not visible to Earth can also reach Earth, following the Parker spiral. However, I'm not sure if this is true. These SEPs are relativistic; surely they are not deflected that much by the magnetic field?

  • $\begingroup$ SEPs during strong flares actually fill up the inner heliosphere and do not necessarily follow the nominal interplanetary magnetic field (IMF) along what is usually consistent with the Parker spiral. However, the SEPs that do follow the magnetic tend to arrive earlier than those diffusing across the field. Some of the STEREO spacecraft observations show SEP enhancements on the opposite side of the sun from the flare source location, which is not along the IMF. $\endgroup$ – honeste_vivere Jun 4 '19 at 7:04
  • $\begingroup$ @honeste_vivere I'm slightly confused by your last sentence, "not along the IMF". Did you mean "along the IMF"? If SEP enhancement is detected on the opposite side of the Sun, isn't that along the IMF (spiral wrapping around)? $\endgroup$ – binaryfunt Jun 4 '19 at 11:14
  • $\begingroup$ No, not in general or even necessary. So far as we can tell, there seems to be a lot of cross-field diffusion and much the inner heliosphere fills up with SEPs during strong solar flares. $\endgroup$ – honeste_vivere Jun 4 '19 at 15:11

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