Meteor head echo plasma and processing collaborations

Background: NASA's Ames Research Center - Chelyabinsk-like Asteroid Entering Earth’s Atmosphere

The meteor head plasma
&
data processing collaborations

Background: NASA's Ames Research Center - Chelyabinsk-like Asteroid Entering Earth’s Atmosphere

The meteor head plasma
&
data processing collaborations

So this was way to big - just wanted a cool intro video

We are going to go to much smaller sizes!

Let's start from the beginning...

The making of a meteor

The making of a meteor

Wide range of parameters

$\approx 10^{-9} - 10^{8}$ kg
$\approx 0 - 74$ km/s
"Fluffy cometary material" - iron

The making of a meteor

One difficultly: the flow regime

The making of a meteor

The flow regime issue

Plot made with https://github.com/danielk333/ablate

The measurement of a meteor

Radar cross section $\mapsto$ meteor plasma frequency "contour line"
meteor plasma "size" $\mapsto$ meteor ablation rate
meteor ablation rate $\mapsto$ mass loss and meteoroid properties
$\int$ mass loss $\mapsto$ "RCS mass"
Other ways: dynamic mass, photometric mass
I have focused on dynamic mass (more on that later)
but, wanted to branch out

The measurement of a meteor

The measurement of a meteor

Conclusion?

Gaussian plasma profiles are not ideal to use
Even in Gaussian simulation, peak meteor plasma density was not well estimated
More examination of dependant parameters needed...

The measurement of a meteor

Dimant, Y. S. & Oppenheim, M. M. 2017 (papers 1 and 2)

Kinetic theory for particles ablated of small fast-moving meteoroids colliding with atmospheric molecules

Conclusion?

$\lambda_T$: the average distance an ablated particle travels from the meteoroid before a collision with an atmospheric particle
$n \propto R^{-1}$ when $R \leq \lambda_T$
$n \propto R^{-2}$ when $R \geq \lambda_T$ behind meteoroid
$n \propto e^{-R^{2/3}}$ when $R \geq \lambda_T$ in front
$n \propto$ solutions between when $R \geq \lambda_T$ and radially around path

The measurement of a meteor

Dimant, Y. S. & Oppenheim, M. M. 2017 (papers 1 and 2)

The measurement of a meteor

The measurement of a meteor

Sugar et al. 2021

Conclusion?

Power-law relationship between ablation rate and radar cross section
However that law is dependant on: radar frequency, mean free path (altitude and velocity), meteor peak plasma frequency, aspect angle, ...
Are there other effects? Is this realistic?
More examination of dependant parameters needed...

The measurement of a meteor

Ok we are getting there - how about observations?

Marshall et al. 2017

The measurement of a meteor

Ok we are getting there - how about observations?

Marshall et al. 2017

Large meteoroids (CMOR is not a HPLA radar), 13-38 MHz

These were head echoes, three frequencies

The measurement of a meteor

$R^{-2}$ fit best

What about smaller particles?

The measurement of a meteor

What about smaller particles?

Close et. al 2002

160 and 422 MHz, HPLA radar (plus some other)
$\approx R^{-1.02} - R^{-1.76}$

Westman et. al 2004

224 and 930 MHz, HPLA radars
No trajectory data, compares height distributions

The measurement of a meteor

Schult et al. 2021

53.5 and 930 MHz, HPLA radars, interferometry

The measurement of a meteor

Schult et al. 2021

Masses between $\approx 10^{-9} - 10^{-6}$ kg

The measurement of a meteor

Conclusion?

Wrong distribution: mass estimates by orders of magnitude
Wrong distribution: density estimates within an order of magnitude
Differential ablation and fragmentation are not yet accounted for
We do not really know when which theory is needed yet

The measurement of a meteor

So as a next step:

Devin decided to revisit the EISCAT VHF / UHF + MAARSY data with our new computational methods

Examining the Altitude Dependence of Meteor Head Echo Plasma Distributions with EISCAT and MAARSY

Devin Huyghebaert, Juha Vierinena, Johan Kero, Ingrid Mann, Ralph Latteck, Daniel Kastinen, Sara Våden, Jorge L. Chau

53.5 and 224 and 930 MHz, HPLA radars

The measurement of a meteor

Huyghebaert et al. 2025

$R^{-\chi}$ model: $\chi \approx 2 - 4$

The measurement of a meteor

Huyghebaert et al. 2025

Interesting deviation from $\chi \leq 2$
HPLA observations, still no trajectory, beam location impact?
Data follows a mean free path dependence as expected
Possible non-linear effects below 95 km

Doing this with EISCAT_3D + other frequencies would be a big step forward!