What’s Going On Inside the Sun? With Lika Guhathakurta

Scientific concepts, discoveries, and nature phenomena covered

Parker Solar Probe (mission status and scientific goals)

• Parker Solar Probe is ongoing and strong, launched in 2018.
• After 24 orbits, it repeatedly reaches its closest approach to the Sun (perihelion).
• It has completed many perihelion passes (speaker mentions finishing around the 28th perihelion in June).
• Key goal: cross the boundary from the “Alfvénic” region into the corona to directly measure how plasma transitions into the solar wind.
• The probe’s closest distance is discussed as ~10 solar radii / ~3.8 million miles, and it moves in and out of the Alfvénic boundary region (not a simple spherical shell).

Trajectory details

• Uses a Venus gravitational assist (gravity assist / braking by Venus gravity), so mission geometry allows it to fall closer to the Sun rather than overshooting.

Helioseismology (using Sun “oscillations” as diagnostics)

• The Sun is not solid, but it has vibrations/oscillations in its interior.
• Helioseismology uses observed surface motions to infer interior properties, especially regions like the convection zone.
• Continuous, near-24/7 observations are crucial to avoid gaps that can cause erroneous inferences.
• Solar Dynamics Observatory (SDO) is cited as enabling high-cadence observations, with a dedicated ground station in New Mexico due to data volume.

Solar wind, the Alfvénic surface/critical point (where escape begins)

• Particle escape is linked to changing conditions:
  • Near the Sun/inner regions (including the corona), particles are influenced by gravity and magnetic fields.
  • At higher temperatures and pressures, particles become solar wind.
• The Alfvénic surface / Alfvén critical point is described as a boundary where particles become less “tethered” and flow out as the solar wind.

Sound and pressure waves in the solar context

• The Sun shows pressure-wave-like oscillations, described as the Sun “ringing” like a musical instrument.
• 5-minute oscillations (known from longstanding observations) are associated with resonant solar oscillation modes relevant to helioseismology.
• Clarification:
  • Ordinary sound cannot propagate through the vacuum of space between the Sun and Earth.
  • We “listen” indirectly by measuring tiny motions of the Sun (an ultrasound metaphor).

Heliosphere and heliopause (the Sun’s “bubble” in interstellar space)

• Heliosphere: region influenced by the Sun’s solar wind and magnetic field, extending through the solar system and bounded by interaction with the local interstellar medium.
• Heliosphere is not symmetric:
  • Different heliospheric boundary distances occur due to solar wind pressure and magnetic field variation.
  • Evidence mentioned: Voyager spacecraft traveled on different directions/latitudes.
• Heliopause: the boundary where solar influence weakens compared to interstellar influence.
  • Mentioned: Voyager 1/2 sensor behavior—at the boundary, the spacecraft could lose the ability to uniquely determine direction to the Sun (sensors “went haywire” when solar signals and galactic signals became comparable).
• Protective role: the heliosphere shields Earth from harmful galactic cosmic radiation.
• Additional boundaries/analogies:
  • Magnetosphere / magnetopause terminology is used as an analogy (Earth’s magnetic bubble vs the Sun’s larger heliosphere bubble).
  • Boundaries are framed as regimes defined by whether gravity, pressure, or magnetic fields dominate.

Solar cycle and solar magnetic field behavior

• The dynamo mechanism in the Sun’s convection zone drives magnetic field generation.
• Key features described:
  • A roughly 11-year solar cycle tied to magnetic activity and sunspots.
  • Sunspot darkness is attributed to strong magnetic fields inhibiting radiation propagation (not necessarily lower total energy).
  • Solar maximum: many sunspots.
  • Solar minimum: fewer or no sunspots, though a basal magnetic field remains.
• A second “beat”:
  • Magnetic polarity flips, so the full magnetic return occurs over ~22 years (two 11-year cycles).

Space weather, coronal mass ejections, geomagnetic storms, and auroras

• Space-weather impacts involve multiple coupled processes:
  • coronal mass ejections (CMEs) and solar storms
  • their interaction with Earth’s magnetosphere, ionosphere, and atmospheric layers
  • effects on satellites, power grids, astronaut radiation exposure, and aviation radiation risk
• Auroras:
  • Caused when solar wind particles interact with Earth’s atmosphere, exciting gas species.
  • Color associations mentioned:
    • Green/red: attributed to oxygen at different altitudes/energies
    • Blue/green: attributed to nitrogen
  • Auroras are described as more visible near the magnetic axis (not geographic north-south).
• Solar storm visibility/strength:
  • NOAA geomagnetic storm category mentioned:
    • Example: May 2024 aurora described as G5, spanning very low latitudes (as far as Florida and the Ladakh region).
    • Example: November 2025 event described as G4 (personal observation story).
• A notable named storm:
  • The “Gannon storm” name is mentioned as being adopted by the White House/space-weather community after aurora-related timing following Dr. Jennifer Gannon’s passing.

Carrington event and modern risk to space assets

• Carrington event (1859): discussed as an extreme solar storm that disrupted telegraph systems.
• Speaker suggests:
  • Based on available evidence, it corresponds to about G5, and may exceed current scaling limits (“we get saturated”).
• Modern satellites and infrastructure could be affected in complex, interacting ways:
  • ionospheric changes
  • power-grid currents
  • energetic particles
  • radiation damage to sensors
  • and more
• Satellite mitigation example:
  • Some systems switch telescopes into safe mode during hazardous conditions.

Example of space-weather impact on Starlink satellites

• Example: late Jan / early Feb 2022
  • A launch attempt occurred during conditions viewed as only mild CME activity.
  • Result: most satellites failed to reach intended orbit due to thermosphere/ionosphere heating, increasing atmospheric drag (insufficient delta-V/propulsion).

Future missions and planned observations (solar wind, heliosphere, and energetic boundary)

• PUNCH (Polarimeter to Unify the Corona and Heliosphere):
  • Constellation of four small satellites in polar Sun-synchronous low Earth orbit.
  • Images solar wind to address gaps: how solar storms originate at the Sun and propagate through the corona to interplanetary space.
• IMAP (Interstellar Mapping and Acceleration Probe):
  • Operates from Lagrange point L1.
  • Studies the heliosphere by sharpening discoveries from IBEX (Interstellar Boundary Explorer).
  • IBEX previously observed a giant ring of high-energy energetic neutral atoms within the heliosphere.
  • IMAP also acts as a space-weather buoy.
• Observing across wavelengths:
  • Need for non-visible bands such as ultraviolet, X-rays, and white light/infrared.
  • Requires space-based platforms because some bands are absorbed by Earth’s atmosphere.

International participation and data sharing

• Multiple agencies/missions mentioned:
  • ESA Solar Orbiter (inclination to view poles)
  • Proba-3 (artificial eclipse using an external coronagraph)
  • India’s Aditya-L1 (sun observation at/near L1, including interior/magnetic-field focus and in-situ instruments)
  • JAXA (Japan) involvement noted
  • China’s Kuafu-L1 referenced
• Data sharing rule mentioned:
  • Except China, information is described as being shared broadly.
• Artemis Accords mentioned as a framework to promote cooperation, including sharing discoveries that could affect safety/security of other missions.

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Researchers or sources featured (as named in the subtitles)

• Lika Guhathakurta
• Neil deGrasse Tyson
• Chuck Nice (StarTalk host)
• Jennifer Gannon (space weather scientist; referenced in personal story)
• NASA
• NOAA
• Lothar Erkans
• Corey Haas
• Monopoly World
• IBEX (Interstellar Boundary Explorer)
• Voyager 1 and Voyager 2
• Solar Dynamics Observatory (SDO)
• Parker Solar Probe
• PUNCH
• IMAP
• ESA (European Space Agency) Solar Orbiter
• Proba-3
• Aditya-L1
• JAXA
• Kuafu-L1
• White House (referenced in naming the storm “Gannon storm”)