You can do this using the application event in aura component.
Step 1: Create an event.The ceEvent.evt component event has one attribute. We’ll use this attribute to pass some data in the event when it’s fired.

<! — c:ceEvent →
<aura:event type=”APPLICATION”>
<aura:attribute name=”message” type=”String”/>
</aura:event>

Step 2: Create a Notifier Component
The c:ceNotifier component uses aura:registerEvent to declare that it may fire the component event.
The button in the component contains an onclick browser event that is wired to the fireComponentEvent action in the client-side controller. The action is invoked when you click the button.

<aura:component>
<aura:registerEvent name=”cmpEvent” type=”c:ceEvent”/>
<h1>Simple Component Event Sample</h1>
<p><lightning:button label=”Click here to fire a component event” onclick=”{!c.fireComponentEvent}” /></p>
</aura:component>

//------below are the JS
/* ceNotifierController.js */
{
fireComponentEvent : function(cmp, event) {
// Get the component event by using the
// name value from aura:registerEvent
var cmpEvent = cmp.getEvent(“cmpEvent”);
cmpEvent.setParams({
“message” : “A component event fired me. “ + “It all happened so fast. Now, I’m here!” });
cmpEvent.fire();
}
}

Create Handler component

<aura:component>
<aura:attribute name=”messageFromEvent” type=”String”/>
<aura:attribute name=”numEvents” type=”Integer” default=”0"/>
<! — Note that name=”cmpEvent” in aura:registerEvent
in ceNotifier.cmp →
<aura:handler name=”cmpEvent” event=”c:ceEvent” action=”{!c.handleComponentEvent}”/>
<! — handler contains the notifier component →
<c:ceNotifier />
<p>{!v.messageFromEvent}</p>
<p>Number of events: {!v.numEvents}</p>
</aura:component>

------controller
({
handleComponentEvent : function(cmp, event) {
var message = event.getParam(“message”);
// set the handler attributes based on event data
cmp.set(“v.messageFromEvent”, message);
var numEventsHandled = parseInt(cmp.get(“v.numEvents”)) + 1;
cmp.set(“v.numEvents”, numEventsHandled);
}
})

please understand the complete dataflow between components here 
https://medium.com/@das.ranbir/lightning-aura-component-279bcf1785cd