HAWC response to the atmospheric electric field activity 1 , - - PowerPoint PPT Presentation

ICRC 2017, Busan Alejandro Lara

HAWC response to the atmospheric electric field activity

Alejandro Lara

1,

Graciela Binimelis de Raga

2 and Olivia Enríquez 1 1Instituto de Geofísica, UNAM 2Centro de Ciencias de la Atmósfera, UNAM

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ICRC 2017 Busan, Korea alara@igeofisica.unam.mx

ICRC 2017, Busan Alejandro Lara

Outline

Motivation HAWC TDC and Hardware scaler systems The HAWC site Electric field measurements Response of HAWC to the atmospheric electricity activity low high medium Two examples of atmospheric electric field and counting rate correlation

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Motivation

HAWC is able to observe heliospheric disturbances as Forbush decreases (FDs) and ground level enhancements (GLEs) In order to study these phenomena we need to correct the data by taking into account the atmospheric effects on the counting rates HAWC low energy (scaler) rates during the FD of Jun 22, 2015 HAWC IMF SW density SW velocity Neutron monitor rates

Motivation

HAWC is able to observe heliospheric disturbances as Forbush decreases (FDs) and ground level enhancements (GLEs) In order to study these phenomena we need to correct the data by taking into account the atmospheric effects on the counting rates In this work we focus in the effects of the atmospheric electricity on the counting rates HAWC low energy (scaler) rates during the FD of Jun 22, 2015 HAWC IMF SW density SW velocity Neutron monitor rates

HAWC

• 22,000 m2 air shower array
• 300 Water Cherenkov detectors (WCD) - 4.5m high, 7.3m diameter

Water Cherenkov Detectors

• 200,000 liters of purified water per WCD
• 4 sensors (photo-multiplier tubes) per WCD

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ICRC 2017, Busan Alejandro Lara

HAWC Scaler Systems

HAWC scaler data are collected by two data acquisition systems (DAQs).:

• The time to digital converters (TDC) or main DAQ system, has a

scaler system which counts the hits, inside a time window of 30 ns, of each PMT and the coincidences of 2, 3 and 4 PMT in each detector, these coincidences are called multiplicity 2, 3 and 4, respectively.

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multiplicity ~energy Mult 2 Mult 3 Mult 4

ICRC 2017, Busan Alejandro Lara

HAWC Scaler Systems

HAWC scaler data are collected by two data acquisition systems (DAQs).:

• The time to digital converters (TDC) or main DAQ system, has a

scaler system which counts the hits, inside a time window of 30 ns, of each PMT and the coincidences of 2, 3 and 4 PMT in each detector, these coincidences are called multiplicity 2, 3 and 4, respectively.

• The second scaler system independently records the hits of each

PMT and we call it hardware (HW) scaler system.

In this study, we use the percentage of the scaler rates referenced to the mean rate value during one hour before the event.

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ICRC 2017, Busan Alejandro Lara

The HAWC site

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HAWC is at a privileged site to study the effects of atmospheric electricity It is at the border of one of the highest lighting incidence areas in Mexico Average spatial distribution of cloud-to-ground lightning density in flashes per square kilometer per year for the period 2006-2012 (Raga et al 2014).. HAWC

ICRC 2017, Busan Alejandro Lara

The HAWC site

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HAWC is at a privileged site to study the effects of atmospheric electricity Is at the border of one of the highest lighting incidence areas The orography forces the formation of thunder-clouds at the site The high altitude makes us able to measure the electric field very close to the clouds HAWC Site 4100m Pico de Orizaba 5636m

Sierra Negra 4640m

ICRC 2017, Busan Alejandro Lara

Electric Field Measurements

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We use the EFM-100 for this work

ICRC 2017, Busan Alejandro Lara

HAWC response to the atmospheric electricity changes

Low electric activity

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Mean count rate of the TDC scaler Multiplicities M - 2 M - 3 M - 4 8” PMTs 10” PMTs The counting rates are not affected by positive fields neither by low-amplitude negative electric field

ICRC 2017, Busan Alejandro Lara

HAWC response to the atmospheric electricity changes

High electric activity

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Mean counting rate of the TDC scaler Multiplicities M - 2 M - 3 M - 4 8” PMTs 10” PMTs lightning activity: cloud to ground (red squares) inter-cloud (purple triangles) The response of the scaler systems during strong electric activity, with close cloud to ground and cloud to cloud discharges, is unstable. We discard this kind of events

ICRC 2017, Busan Alejandro Lara

HAWC response to the atmospheric electricity changes

Moderated electric activity

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Mean counting rate of the HW scaler system, each available channel is plotted in different color. lightning activity: cloud to ground (red squares) inter-cloud (purple triangles) There is a clear distinction between the spikes due to the lightning discharges and the slow and well correlated, scaler enhancements due to the negative electric field increases.

Spikes

ICRC 2017, Busan Alejandro Lara

HAWC slow response to atmospheric negative electric field increases example 1, rate enhancement of 6%

Two examples of scaler enhancement during increases of electric field where selected due to the good (not saturation) measurement of the electric field.

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Mean counting rate of the TDC scaler Multiplicities during May 26, 2015 Mean counting rate of the HW scaler system during May 26, 2015.

ICRC 2017, Busan Alejandro Lara

HAWC slow response to atmospheric negative electric field increases example 2 - rate enhancement of 1 %

It is important to note the correlated behaviour of all available channels.

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Mean counting rate of the TDC scaler Multiplicities during Sep 3, 2015. Mean counting rate of the HW scaler system during Sep 3, 2015. .

ICRC 2017, Busan Alejandro Lara

HAWC slow response to increases of the atmospheric negative electric field and the atmospheric variables (example 1)

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. The ambient pressure has not effect in this enhancement The ambient temperature has not effect in this enhancement There were humidity at the site There were rain close to the time of the enhancement The solar irradiance was low, showing the presence

• f clouds

The electric field changes significantly during the enhancement

ICRC 2017, Busan Alejandro Lara

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. The ambient pressure has not effect in this enhancement The ambient temperature has not effect in this enhancement There were humidity at the site There were rain close to the time of the enhancement The solar irradiance was low, showing the presence

• f clouds

The electric field changes significantly during the enhancement

HAWC slow response to increases of the atmospheric negative electric field and the atmospheric variables (example 2)

Relationship between the scaler rate and the electric field strength cross correlation lag

Mult 2 Mult 3 Mult 4 8” PMTs 10” PMTs There may be a phase difference between the electric field and the scaler rates electric field mill 150 m Sep 03, 2015 May 26, 2015

(min) (min)

ICRC 2017, Busan Alejandro Lara

Relationship between TDC scaler enhancements and negative electric field magnitude (example 1)

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There is no correlation between the pressure nor temperature and the enhancements Cross correlation coefficients There is a good correlation between the electric field and the TDC enhancements

mult 2 mult 3 mult 4 8” PMT 10” PMT May 26, 2015.

May 26, 2015

ICRC 2017, Busan Alejandro Lara

Relationship between TDC scaler enhancements and negative electric field magnitude (example 1)

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There is no correlation between the pressure nor temperature and the enhancements Cross correlation coefficients There is a good correlation between the electric field and the TDC enhancements

mult 2 mult 3 mult 4 8” PMT 10” PMT May 26, 2015.

May 26, 2015 Regular correlations

ICRC 2017, Busan Alejandro Lara

Relationship between TDC scaler enhancements and negative electric field magnitude (example 2)

.

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There is no correlation between the pressure nor temperature and the enhancements Cross correlation coefficients There is a good correlation between the electric field and the TDC enhancements But we need more events to quantify the relationship Sep 03, 2015

mult 2 mult 3 mult 4 8” PMT 10” PMT May 26, 2015.

ICRC 2017, Busan Alejandro Lara

Summary - Discussion - Outlook

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• HAWC is able to detect solar transients as Forbush Decreases and GLEs,

although it is necessary to correct the data for the atmospheric electricity influence

ICRC 2017, Busan Alejandro Lara

Summary - Discussion - Outlook

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• HAWC is able to detect solar transients as Forbush Decreases, although it is

necessary to correct the data for the atmospheric electricity influence

• The observed, well correlated, rate increases during episodes of high negative

electric electric field may be caused by:

• induced noise at PMTs
• acceleration of particles (runaway electrons)
• enhanced secondary CR flux (muons)
• It is necessary to further investigate these effects to determine the cause of the

rate enhancements during atmospheric electric activity (outgoing work)

ICRC 2017, Busan Alejandro Lara

Summary - Discussion - Outlook

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• HAWC is able to detect solar transients as Forbush Decreases, although it is

necessary to correct the data for the atmospheric electricity influence

• The observed, well correlated, rate increases during episodes of high negative

electric electric field may be caused by:

• induced noise at PMTs
• acceleration of particles (runaway electrons)
• enhanced secondary CR flux (muons)
• It is necessary to further investigate these effects to determine the cause of the

rate enhancements during atmospheric electric activity (outgoing work)

• Wait for solar activity

Thanks!