Advancing Magnetoseismology by Ground-based Magnetometer Networks

Peter Chi (UCLA; NASA/GSFC)

Quo Vadis Workshop @ 2016 GEM-CEDAR

180oW 120

oW 60

oW 0

o 60

oE 120

oE 180

oW

80oS

40oS

0o

40oN

80oN

McMAC Falcon THEMIS IGPP-LANL MEASURE SAMBA AMBER

CARISMA

AUTUMN

MACCS

GIMA

AGO

MAGDAS

AAMN

IMAGE DTU DFZ SEGMA AAL-PIP

AMBER (new)

ULTIMA: December 2014

L=10L=8L=6L=4

L=2

L=1

L=2

L=4L=6L=8L=10

ULTIMA kick-off meeting at UCLA (November 17, 2006)

Russell Yumoto Angelopoulos

Fraser Chi Mann

Moldwin

Milling

(17 member arrays; 250+ stations)

Field Line Resonance (FLR) Sounding of the Magnetosphere

175oW 150

oW 125

oW 100

oW 75

oW 50

oW

12oN

24oN

36oN

48oN

60oN

72oN

Successful stations pairs for detecting FLR signals

Turning magnetic field measurements into plasma density measurements

Monitoring Plasmaspheric Density by Ground-based Magnetometers

log10 (m)

[a.m.u. cm3]

0 0.5 10

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

1

1.5

2

2.5

3

3.5

4

2007-Oct-25

175oW 150

oW 125

oW 100

oW 75

oW 50

oW

12oN

24oN

36oN

48oN

60oN

72oN

Video

Magnetoseismology 1: Field Line Resonance Sounding of the Magnetosphere

• A mature method well tested by previous more localized magnetometer projects (e.g. US McMAC and European PLASMON chains).

• Knowledge Gap: (1) Processes that result in the longitudinal structure at the plasmasphere boundary layer during quiet times. (2) The plasma exchange between ionosphere and plasmasphere during storm times.

• Required Instrumentation (and gap): (1) A dense 2-D magnetometer network of ~200 stations in North America; There are ~100 stations now; Existing stations still require modest support to continue. (2) Magnetometers on buoys? (Technology not ready)

• Space Weather Implications: The plasma mass density obtained through FLR magnetoseismology can be valuable for understanding the cold plasma reservoir, which varies with space weather activity and can affect particle energization.

5

6

Magneto-seismology 2: Remote sensing of impulsive processes

6

Earthquakes and seismic waves Sudden impulses

Substorm onsets

1. Interior structure of Earth 2. Center of Earthquake

The onset location is important in understanding

substorm generation.

The impulse can reveal density distribution in

the dayside magnetosphere.

Travel-time Analysis for Substorm Onsets (Magnetotail)

• Locations of substorm onsets: 18-20 Re in the tail direction

• Substorm onset starts in the magnetotail ~ 100 --200 sec before the first auroral brightening.

• Results from several events are consistent with the reconnection model for substorms.

7

Observations

Inversion

Arrival Time

Gro

und

Magneto

mete

rs

low lat.

high lat.

Forward modeling of signal propagation in the magnetotail

Magnetoseismology 2: Travel time of impulsive processes from the magnetotail

• Travel-time magnetoseismology has presented initial successes in observing the impulsive processes and the associated environment of the magnetosphere.

• Knowledge Gaps: Impulse propagation in the magnetotail – what physics should be included? How the field and plasma conditions affect propagation?

• Observation Gaps: Both ground-based and spacecraft magnetic field measurements are relevant. Need model with relevant physics to determine observation gaps. An ISSI team on magnetoseismology has been established to determine where are the most effective locations for new observations.

• Space Weather Implications: (1) To locate and time generation of impulsive processes (reconnection, current disruption instabilities, etc.) related to generation of substorms. (2) Results from travel-time magnetoseismology can be ingested to future updates of space weather models to aid forecasting.

8

Two Seismic Methods in All Seismologies

Seismology Helio-/Astero- Seismology

Magneto- seismology

Travel-time Method

Normal-mode Method

9

A new ISSI Team on magneto-seismology has just started.