Geospace Variability through the Solar Cycle

John FosterMIT Haystack Observatory

Introduction – My Geospace Background(Who is the Lecturer? Why will it matter?)

• Antarctica - Relativistic wave-particle – M/I coupling

• Canada – International Satellite for Ionospheric Study (ISIS)

• Utah State Univ. - Alaska incoherent scatter radar studies of auroral disturbances and

electrodynamics

• Yosemite conferences – broad topics in Geospace system science

• MIT - Radio-physics research investigating M-I-T phenomena from the ground and space

• Van Allen Probes - Ionospheric effects on magnetospheric processes

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• I am data/observations oriented. I am NOT a modeler

• Today we’ll see what the data say about Geospace variability and interconnections

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Haystack Observatory

Millstone HillObservatory

Firepond OpticalFacility

Millstone Hill Radar

MIT Haystack Observatory ComplexWestford, Massachusetts

Established 1956

Radio AstronomyAtmospheric ScienceSpace Surveillance

Radio ScienceEducation and Public Outreach

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Geospace VariabilityOutline – Lecture #1

• What is Geospace?• Solar Cycle – Sunspots & EUV Solar Output• Cycles in the Ionosphere• Seasonal, Local Time and Activity Effects• M-I Drivers of the Thermosphere• Solar Cycle – Solar Activity• Coronal Mass Ejections – Shocks• Coronal Holes and High-Speed Streams

- Solar Rotation – Periodic Disturbances

What is Geospace?

• Geospace is the interconnected environment of our planet.

• The region of outer space near Earth, including the upper atmosphere, ionosphere and magnetosphere.

• It includes the Sun’s photosphere, chromosphere and corona, the solar wind, Earth's magnetosheath, magnetosphere, thermosphere, ionosphere and mesosphere.

• The Geospace system also encompasses the lower atmosphere, oceans, solid earth & Earth’s magnetic field

Don’t forget the Biosphere & Man

• Major defining elements: Earth’s magnetic field, Earth’s atmosphere, and the Sun’s electromagnetic & particle emissions

The CoupledGeospace System

(top) Solar Minimum (bottom) Solar Maximum NOTE different altitude scales

Millstone Hill Incoherent Scatter RadarMid-Latitude Ionosphere

(50-yr database of local observations)

Auroral IonosphereMid-Latitude Ionosphere

Ionospheric Trough

Cycles in the Ionosphere

Diurnal – Solar production on dayside

Latitudinal – Insolation, dipolar magnetic field, M-I coupling

Seasonal – Solar inclination and interhemispheric winds, SW – magnetosphere coupling

Solar Cycle: Variations in solar output (F10.7 flux) Solar activity effects

Statistical empirical models derived from 50 years of incoherent scatter radar observations

Millstone Hill – mid/sub-auroral latitudeArecibo – low latitude (near-equatorial processes)

Millstone Hill Ap = 15Winter

Summer

F10.7 = 70

F10.7 = 150

Millstone Hill Ap = 150Winter

Summer

F10.7 = 70

F10.7 = 150

Arecibo Ap = 15Winter

Summer

F10.7 = 70

F10.7 = 150

Arecibo Ap=150Winter

Summer

F10.7 = 70

F10.7 = 150

GPS transmissions sample the ionosphere and plasmasphere to ~20,000 km. Dual-frequency Faraday Rotation Observations give TEC (Total Electron Content)

TEC is a measure of integrated density in a 1 m2 column

1 TEC unit = 1016 electrons m-2

Hundreds of Ground-Based

Receivers

~30 satellites in High Earth

Orbit

TEC Sampled Continuously along Each Satellite-

Receiver Path

20 December 2009 Extended Solar Minimum max log TEC = 1.5

20 December 2013 Solar Maximum max log TEC = 1.8

Field-Aligned Currents Link the Magnetosphere and the Ionosphere

Joule dissipation of ionospheric currents is a major ionospheric energy source.

Joule Heating Rate SPE2

is determined from individual observations of electric field and Pedersen conductivity over the lifetime of the AE-C satellite. [Foster et al, 1983]

The contribution of solar-produced dayside conductivity is important.

Joule energy deposition affects the dynamical properties of the thermosphere – winds, temperature, and composition.

<SPE2> <SP><E2>

SP

E2

Seasonal and Activity Variation of Joule Heating - AE-C Data

The effects of Solar activity propagate to Earth both promptly (x-ray and radio bursts) and via perturbations in solar wind particle fluxes and magnetic field.

Geomagnetic disturbances result from interactions of the solar wind with Earth’s magnetosphere and involve the coupled geospace system.

Geomagnetic activity follows the solar cycle.

Sunspot number and area indicate the level of magnetic perturbation in the solar photosphere. Associated solar flares and eruptions drive the geospace disturbances.

The major contributers to the solar wind disturbances and severe geospace storms exhibit defined solar cycle dependencies.

Coronal mass ejections (CMEs) are most numerous during solar maximum, but persist into the early declining phase of the solar sunspot cycle.

Coronal holes and resulting solar wind high speed streams are associated with the quieting phase of the solar cycle extending into solar minimum.

Coronal Mass EjectionSolar Wind Shock

Geomagnetic Storm

Solar Wind Shock

Propagation of Shock-Induced Pulsethrough the Inner Magnetosphere

[M. K. Hudson et al., JGR, 2015]

Energy & L Dependence of Drift Echoes

3.6 MeV

90 keV

350 keV

RBSP-B

RBSP-A

ULF Ringing

Universal Time

CME occurrence persists into declining phase of solar cycle

Coronal mass ejections reach velocities between ~100 to ~ 3,200 km/s with an average speed of~490 km/. These speeds correspond to transit times from the sun out to the

mean radius of Earth's orbit of about 15 days to 13 hours and 3.5 days (average).

The frequency of CMEs depends on the phase of the solar cycle: from about one every fifth day near the solar minimum to 3.5 per day near the solar maximum.

CMEs

Sunspots

Solar RotationCoronal Holes

High-Speed Streams

Solar RotationCoronal Holes

High-Speed StreamsPeriodic Activity

RATE Experiment

End of Part I